nuclear marine propulsion

NUCLEAR MARINE PROPULSION
© M. Ragheb
11/11/2010
1. INTRODUCTION
Three trends are shaping the future of naval ship technology: the all electrical ship,
stealth technology and littoral vessels.
Littoral Combat Ships are designed to operate closer to the coastlines than existing
vessels such as destroyers. Their mission is signal intelligence gathering, stealth insertion of
special forces, mine clearance, submarine hunting and humanitarian relief. The all-electric ship
propulsion concept was adopted for the future surface combatant power source. It would
encompass new weapon systems such as modern electromagnetic rail-guns and lasers under
development.
The largest experience in operating nuclear power plants since the late 1950s has been in
nuclear marine propulsion, particularly aircraft carriers (Fig. 1) and submarines. The nuclear
powered vessels comprise about 40 percent of the USA Navy's combatant fleet, including the
entire sea based strategic nuclear deterrent. All the USA Navy’s operational submarines and
over half of its aircraft carriers are nuclear powered. The USA Navy as of 2008 operated 99
vessels powered by nuclear reactors including 10 nuclear powered aircraft carriers and 71
submarines. It has operated nuclear powered ships for more than 50 years. As of 2001, about
235 naval reactors had been built at a unit cost of about $100 million for a submarine and $200
for an aircraft carrier.
The main considerations here are that nuclear powered submarines do not consume oxygen
like conventional power plants, and that they have large endurance or mission times before fuel
resupply, limited only by the available food and air purification supplies on board.
Figure 1. Nuclear aircraft carrier USS Theodore Roosevelt, Nimitz Class CVN71, powered with
two A4W (A for Aircraft carrier, 4 for fourth generation and W for Westinghouse) nuclear
reactors, crossing the Suez Canal, Egypt, during the first Gulf War, January 1991.
By 2002, the USA Navy operated 53 attack submarines (SSN) and 18 ballistic missile
submarines (SSBN). These used by 1999 about 129 nuclear reactors exceeding the number of
commercial power plants at 108. The mission for nuclear powered submarines is being
redefined in terms of signal intelligence gathering and special operations.
During World War II, submarines used diesel engines that could be run on the water surface,
charging a large bank of electrical batteries. These could later be used while the submarine is
submerged, until discharged. At this point the submarine had to resurface to recharge its
batteries and become vulnerable to detection by aircraft and surface vessels.
Even though special snorkel devices were used to suck and exhaust air to the submarine
shallowly submerged below the water's surface, a nuclear reactor provides it with a theoretical
infinite submersion time. In addition, the high specific energy, or energy per unit weight of
nuclear fuel, eliminates the need for constant refueling by fleets of vulnerable tankers following
a fleet of surface or subsurface naval vessels. On the other hand, a single refueling of a nuclear
reactor is sufficient for long intervals of time.
With a high enrichment level of 93 percent, capable of reaching 97.3 percent in U235, naval
reactors, are designed for a refueling after 10 or more years over their 20-30 years lifetime,
whereas land based reactors use fuel enriched to 3-5 percent in U235, and need to be refueled
every 1-1 1/2 years period. New cores are designed to last 50 years in carriers and 30-40 years in
submarines, which is the design goal of the Virginia class of submarines.
Burnable poisons such as gadolinium or boron are incorporated in the cores. These allow a
high initial reactivity that compensates for the build up of fission products poisons over the core
lifetime, as well as the need to overcome the reactor dead time caused by the xenon poison
changes as a result of operation at different power levels.
Naval reactors use high burn up fuels such as uranium-zirconium, uranium-aluminum, and
metal ceramic fuels, in contrast to land-based reactors which use uranium dioxide UO2. These
factors provide the naval vessels theoretical infinite range and mission time. For these two
considerations, it is recognized that a nuclear reactor is the ideal engine for naval propulsion.
A compact pressure vessel with an internal neutron and gamma ray shield is required by the
design while maintaining safety of operation. Their thermal efficiency is lower than the thermal
efficiency of land based reactors because of the emphasis on flexible power operation rather than
steady state operation, and of space constraints.
Reactor powers range from 10 MWth in prototypes to 200 MWth in large subsurface vessels,
and 300 MWth in surface ships. Newer designs use jet pump propulsion instead of propellers,
and aim at an all electrical system design, including the weapons systems such as
electromagnetic guns.
2. NUCLEAR NAVAL VESSELS
Jules Verne, the French author in his 1870 book: “20,000 Leagues Under the Sea,”
related the story of an electric submarine. The submarine was called the “Nautilus,” under its
captain Nemo. Science fiction became reality when the first nuclear submarine built by the
American Navy was given the same name. Figure 2 shows a photograph of the Nautilus, the first
nuclear powered submarine.
Construction of the Nautilus (SSN-571) started on June 14, 1952, its first operation was
on December 30, 1954 and it reached full power operation on January 13, 1955. It was
commissioned in 1954, with its first sea trials in 1955. It set speed, distance and submergence
records for submarine operation that were not possible with conventional submarines. It was the
first ship to reach the North Pole. It was decommissioned in 1980 after 25 years of service,
2,500 dives, and a travelled distance of 513,000 miles. It is preserved at a museum at Croton,
Connecticut.
Figure 2. The "Nautilus", the first nuclear powered submarine.
Figure 3 shows the experimental setup S1W prototype for the testing of the Nautilus’s
nuclear reactor built at the Idaho Nuclear Engineering and Environmental Laboratory (INEEL) in
1989.
The advantage of a nuclear engine for a submarine is that it can travel long distances
undetected at high speed underwater avoiding the surface wave resistance, without refueling.
Unlike diesel engine driven submarines, the nuclear engine does not need oxygen to produce its
energy.
The reactor for the Nautilus was a light water moderated, highly enriched in Uranium 235
core, with zirconium clad fuel plates. The high fuel enrichment gives the reactor a compact size,
and a high reactivity reserve to override the xenon poison dead time. The Nautilus beat
numerous records, establishing nuclear propulsion as the ideal driving force for the world's
submarine fleet. Among its feats was the first underwater crossing of the Arctic ice cap. It
traveled 1,400 miles at an average speed of 20 knots. On a first core without refueling, it
traveled 62,000 miles.
Zirconium has a low neutron absorption cross section and, like stainless steel, forms a
protective, invisible oxide film on its surface upon exposure to air. This oxide film is composed
of zirconia or ZrO2 and is on the order of only 50 to 100 angstroms in thickness. This ultra thin
oxide prevents the reaction of the underlying zirconium metal with virtually any chemical
reagent under ambient conditions. The only reagent that will attack zirconium metal at room
temperature is hydrofluoric acid, HF, which will dissolve the thin oxide layer off of the surface
of the metal and thus allow HF to dissolve the metal itself, with the concurrent evolution of
hydrogen gas.
Another nuclear submarine, the Triton reenacted Magellan's trip around the Earth.
Magellan traveled on the surface, while the Triton did it completely submerged.
Figure 3. Experimental setup for testing Nautilus type naval reactors at the Idaho National
Engineering Laboratory, INEL, 1989.
3. NAVAL REACTOR DEVELOPMENT
INTRODUCTION
There have been more reactor concepts investigated in the naval propulsion area by
different manufacturers and laboratories than in the civilian field, and much can be learned from
their experience for land applications.
According to the type of vessel they power they have different first letter designations: A
for Aircraft carrier, C for Cruiser, D for Destroyer or Cruiser and S for Submarine.
They are also designated with a last letter according to the designer institution or lead
laboratory: B for Bechtel, C for Combustion Engineering, G for General Electric and W for
Westinghouse.
A middle number between the first and last letter refers to the generation number of the
core design. For instance, the A1B is the first generation of a core design for aircraft carriers
with Bechtel operating the lead laboratory for the design.
Naval reactors designs use boron as a burnable poison. The vertical direction doping
provides a long core life, and the radial doping provides for an even power and fuel burnup
distribution.
STR OR S1W PRESSURIZED WATER REACTOR DESIGN
The Westinghouse Electric Corporation under contract to the USA Navy constructed,
tested and operated a prototype pressurized water reactor submarine reactor plant. This first
reactor plant was called the Submarine Thermal Reactor, or STR. On March 30, 1953, the STR
was brought to power for the first time and the age of naval nuclear propulsion was born. In
1953 it achieved a 96 hours sustained full power run simulating a crossing of the Atlantic Ocean.
The second S1W core sustained in 1955 a 66 days continuous full power simulating a high speed
run twice around the globe.
The STR was redesigned as the first generation submarine reactor S1W, which became
critical on March 30, 1953, was the prototype of the USS Nautilus (SSN 571) reactor and was
followed in the middle to late 1950s by the Aircraft carrier A1W, the prototype of the aircraft
carrier USS Enterprise plant.
Westinghouse's Bettis Atomic Power Laboratory was assigned the responsibility for
operating the reactor it had designed and built, hence the W in the name. The crew was
increasingly augmented by naval personnel as the cadre of trained operators grew
The fuel elements are sandwich plates made of U and Zr and clad in Zr. The maximum
temperature in the fuel was 645 oF and the sheath temperature was 551 oF with an average cycle
time of 600 hours or just 600 / 24 = 25 days. The reactor temperature is limited by the pressure
needed to prevent boiling, necessitating high pressure vessels, piping and heat exchangers. The
steam was generated at a relatively low pressure. A high level of pumping power was required,
and the fuel was costly. However this design had few hazards, has been proven in service, and
an expensive moderator was not needed.
The S1C reactor used an electric drive rather than a steam turbine like in the subsequent
S5W reactor design rated at 78 MWth and a 93 percent U235 enriched core that was the standard
in the 1970s. The S6G reactor plant was rated at 148 MWth and the D2W core was rated at 165
MWth.
The S6G reactor is reported to be capable of propelling a Los Angeles class submarine at
15 knots or 27.7 km/hr when surfaced and 25 knots or 46.3 km/hr while submerged.
The Sea wolf class of submarines was equipped with a single S6W reactor, whereas the
Virginia class of submarines is expected to be equipped with an S9G reactor.
The higher achievable submerged speed is due to the absence of wave friction underwater
suggesting that submarine cargo ships would offer a future energy saving alternative to surface
cargo ships.
A1W PROTOTYPE PLANT
The A1W prototype plant was started in 1956 for surface ships using two pressurized
water reactors. The plant was built as a prototype for the aircraft carrier USS Enterprise (CVN
65), which was the first nuclear-powered aircraft carrier. Power operation of the A1W plant
started in October of 1958. It was the first nuclear propulsion plant to have two reactors
powering one ship propeller shaft through a single geared turbine propulsion unit.
In the A1W and A2W designs, the coolant was kept at a temperature between 525-545 °F
or 274-285 °C. In the steam generators, the water from the feed system is converted to steam at
535 °F or 279 °C and a pressure of about 600 psi or 4 MPa . The reactor coolant water was
recirculated by four large electric pumps for each reactor.
The steam was channeled from each steam generator to a common header, where the
steam is then sent to the main engine, electrical generators, aircraft catapult system, and various
auxiliaries. The main propulsion turbines are double ended, in which the steam enters at the
center and divides into two opposing streams.
The main shaft was coupled to a reduction gear in which the high rotational velocity of
the turbine shaft is stepped down to a usable turn rate for propelling the ship.
In the A3W reactor design used on the USS John F. Kennedy a 4 reactor design is used.
In the A4W design with a life span of 23 years on the Nimitz class carriers only two reactors per
ship are used with each providing 104 MWth of power or 140,000 shaft HP. The A1B is also a
two reactor design for the Gerald R. Ford class of carriers.
SIR OR S1G INTERMEDIATE FLUX BERYLLIUM SODIUM COOLED
REACTOR
This reactor design was built by the General Electric (GE) Company, hence the G
designation. The neutron spectrum was intermediate in energy. It used UO2 fuel clad in
stainless steel with Be used as a moderator and a reflector. The maximum temperature in the
fuel could reach 1,700 +/- 300 oF with a maximum sheath temperature of 900 oF, with a cycle
time of 900 hours or 900 / 24 = 37.5 days.
A disadvantage is that the coolant becomes activated with the heat exchangers requiring
heavy shielding. In addition Na reacts explosively with water and the fuel element removal is
problematic. On the other hand high reactor and steam temperatures can be reached with a
higher thermal efficiency. A low pressure is used in the primary system.
Beryllium has been used as a moderator in the Sea Wolf class of submarines reactors. It
is a relatively good solid moderator, both from the perspectives of slowing down power and of
the moderating ratio, and has a very high thermal conductivity. Pure Be has good corrosion
resistance to water up to 500 oF, to sodium to 1,000 oF, and to air attack to 1,100 oF. It has a
noted vapor pressure at 1,400 oF and is not considered for use much above 1,200 oF even with an
inert gas system. It is expensive to produce and fabricate, has poor ductility and is extremely
toxic necessitating measures to prevent inhalation and ingestion of its dust during fabrication.
A considerably small size thermal reactor can be built using beryllium oxide as a
moderator. It has the same toxicity as Be, but is less expensive to fabricate. It can be used with
a sodium cooled thermal reactor design because BeO is corrosion resistant to sodium. It has
similar nuclear properties to Be, has a very high thermal conductivity as a ceramic, and has a
good resistance to thermal shock. It can be used in the presence of air, sodium and CO 2. It is
volatile in water vapor above 1,800 oF. In its dense form, it resists attack by Na or Na-K at a
temperature of 1,000 oF. BeO can be used as a fuel element material when impregnated with
uranium. Low density increases its resistance to shock. A BeO coating can be applied to cut
down on fission products release to the system.
The USS Seawolf submarine, initially used a Na cooled reactor that was replaced in 1959
by a PWR to standardize the fleet, because of superheater bypass problems causing mediocre
performance and as a result of a sodium fire. The steam turbines had their blades replaced to use
saturated rather than superheated steam. The reactor was housed in a containment vessel
designed to contain a sodium fire.
The eighth generation S8G reactor was capable of operating at a significant fraction of
full power without reactor coolant pumps. The S8G reactor was designed by General Electric for
use on the Ohio class (SSGN/SSBN-726) submarines. A land based prototype of the reactor
plant was built at Knolls Atomic Power Laboratory at Ballston Spa, New York. The prototype
was used for testing and crew training throughout the 1980s. In 1994, the core was replaced with
a sixth generation S6W Westinghouse reactor, designed for the Sea Wolf class submarines.
SC-WR SUPER CRITICAL WATER REACTOR
The Super Critical Water Reactor (SC-WR) was considered with an intermediate energy
neutron spectrum. The fuel was composed of UO2 dispersed in a stainless steel matrix. It
consisted of 1 inch square box with parallel plates and sine wave filters with a type 347 stainless
steel cladding 0.007 inch thick. The maximum temperature in the fuel reached 1,300 oF with an
average cycle time of 144 hours or 144 / 24 = 6 days.
The materials for high pressure and temperature and the retention of mechanical seals and
other components were a service problem.
The water coolant reached a pressure of 5,000 psi. The high pressure and temperature
steam results in a high cycle efficiency, small size of the reactor with no phase change in the
coolant.
ORGANIC COOLED AND MODERATED REACTOR
The Organic Cooled and Moderated Reactor has been considered as a thermal neutron
spectrum shipboard power plant.
The rectangular plates fuel clad in aluminum can be natural uranium since the Terphenyl
organic coolant can have good moderating properties. The cladding temperature can reach 800
o
F with an average cycle time of 2,160 hours or 2,160 / 24 = 90 days.
The overall heat transfer coefficient of the coolant is low with the formation of polymers
under irradiation that require a purification system. The advantages are negligible corrosion and
the achievement of low pressure at a high temperature.
LEAD COOLED FAST REACTORS
The alpha class of Russian submarines used an alloy of Pb-Bi 45-50 percent by weight
cooled fast reactors. The melting point of this alloy is 257 oF. They faced problems of corrosion
of the reactor components, melting point, pump power, polonium activity and problems in fuel
unloading.
Refueling needed a steam supply to keep the liquid metal molten. Bismuth leads to
radiation from the activated products, particularly polonium. An advantage is that at
decommissioning time, the core can be allowed to cool into a solid mass with the lead providing
adequate radiation shielding.
This class of submarines has been decommissioned.
NATURAL CIRCULATION S5G PROTOTYPE
The S5G reactor was a prototype that operated in either a forced or natural circulation
flow mode. The plant had two coolant loops and two steam generators. It had to be designed
with the reactor vessel situated low in the boat and the steam generators high in order for natural
circulation of the coolant to be developed and maintained.
This nuclear reactor was installed both as a land based prototype at the Nuclear Power
Training Unit, Idaho National Engineering Laboratory near Idaho Falls, Idaho, and on board the
USS Narwhal (SSN-671), now decommissioned.
The prototype plant in Idaho was given a rigorous performance check to determine if
such a design would work for the USA Navy. It was largely a success, although the design never
became the basis for any more fast attack submarines besides the Narwhal. The prototype testing
included the simulation of essentially the entire engine room of an attack submarine. By floating
the plant in a large pool of water, the whole prototype could be rotated along its long axis to
simulate a hard turn. This was necessary to determine whether natural circulation would
continue even during hard maneuvers, since natural circulation is dependent on gravity.
The USS Narwhal had the quietest reactor plant in the USA naval fleet. Its 90 MWth
reactor plant was slightly more powerful than the other fast attack USA nuclear submarines of
that era such as the third generation S3G and the fifth generation S5W. The Narwhal contributed
significantly to the USA effort during the Cold War. With its quiet propulsion and the pod
attached to its hull, it used a towed sonar array and possibly carried a Remotely Operated
Vehicle (ROV) for tapping into communication cables and maintaining a megaphones tracking
system at the bottom of the oceans.
It was intended to test the potential contribution of natural circulation technology to
submarine noise suppression by the avoidance of forced flow pump cooling. The reactor
primary coolant pumps are one of the primary sources of noise from submarines in addition to
the speed reduction gearbox and cavitation from the propeller. The elimination of the coolant
pumps and associated equipment would also reduce mechanical complexity and the space
required by the propulsion equipment.
The S5G was the direct precursor to the eighth generation S8G reactor used on the Ohio
class ballistic missile submarines; a quiet submarine design.
The S5G was also equipped with coolant pumps that were only needed in emergencies to
attain high power and speed. The reactor core was designed with very smooth paths for the
coolant. Accordingly, the coolant pumps were smaller and quieter than the ones used by the
competing S5W core, a Westinghouse design. They were also fewer in numbers. In most
situations, the submarine could be operated without using the coolant pumps, useful for stealth
operation. The reduction in electrical requirements enabled this design to use only a single
electrical turbine generator plant.
The S8G prototype used natural circulation allowing operation at a significant fraction of
full power without using the reactor pumps, providing a silent stealth operation mode.
To further reduce engine plant noise, the normal propulsion setup of two steam turbines
driving the propeller screw through a reduction gear unit was changed instead to one large
propulsion turbine without reduction gears. This eliminated the noise from the main reduction
gears, but at the expense of a large main propulsion turbine. The turbine was cylindrical, about
12 feet in diameter and 30 feet in length. This large size was necessary to allow it to turn slowly
enough to directly drive the screw and be fairly efficient in doing so. The same propulsion setup
was used on both the USS Narwhal and its land based prototype.
FAIL SAFE CONTROL AND LOAD FOLLOWING S7G DESIGN
The S7G core was controlled by stationary gadolinium clad tubes that were partially
filled with water. Water was pumped from the portion of the tube inside the core to a reservoir
above the core, or allowed to flow back down into the tube. A higher water level in the tube
within the core slowed down the neutrons allowing them to be captured by the gadolinium tube
cladding rather than the uranium fuel, leading to a lower power level.
The system had a fail safe control system. The pump needed to run continually to keep
the water level pumped down. Upon an accidental loss of power, all the water would flow back
into the tube, shutting down the reactor.
This design also had the advantage of a negative reactivity feedback and a load following
mechanism. An increase in reactor power caused the water to expand to a lower density
lowering the power. The water level in the tubes controlled average coolant temperature, not
reactor power. An increase in steam demand resulting from opening the main engines throttle
valves would automatically increase reactor power without action by the operator.
S9G HIGH ENERGY DENSITY CORE
The S9G is a PWR built by General Electric with increased energy density, and new plant
components, including a new steam generator design featuring improved corrosion resistance
and a reduced life cycle cost. This reactor in the Virginia class SSN-774 submarines is designed
to operate for 33 years without refueling and last the expected 30 year design life of a typical
submarine.
The higher power density decreases not only size but also enhances quiet operation
through the elimination of bulky control and pumping equipment. It would be superior to any
Russian design from the perspective of noise reduction capability, with 30 units planned to be
built.
Table 1. Power ratings of naval reactor designs.
Reactor type
A2W
A4W/A1G
C1W
D2G
S5W
S5G
S6W
S8G
S9G
Rated power
shaft horse power,
[MW]*
[shp]
35,000
26.1
140,000
104.4
40,000
29.8
35,000
26.1
15,000
11.2
17,000
12.7
35,000
26.1
35,000
26.1
40,000
29.8
*1 shp = 745.6999 Watt = 0.7456999 kW
EXPENDED CORE FACILITY, ECF
The Expended Core Facility was built in 1957. It was used to examine expended naval
reactor fuel to aid in the improvement of future generations of naval reactors. In the middle
1960s, the fifth generation S5G, the prototype of the submarine USS Narwhal reactor, and
predecessor to the reactor plant used to propel the Trident Fleet Ballistic Missile Submarines,
was built and placed in service by the General Electric Company.
The Expended Core Facility ECF was built to examine and test fuel from nuclear
powered vessels, prototype plants, and the Shippingport Power Plant. It has examined specimens
of irradiated fuel that were placed in a test reactor, such as the Advanced Test Reactor (ATR).
The information from detailed study of this fuel has enabled the endurance of naval
nuclear propulsion plants to be increased from two years for the first core in Nautilus to the
entire 30+ year lifetime of the submarines under construction today.
It originally consisted of a water pool and a shielded cell with a connecting transfer canal.
It has been modified by the addition of three more water pools and several shielded cells. The
water pools permit visual observation of naval spent nuclear fuel during handling and inspection
while shielding workers from radiation. The shielded cells are used for operations which must
be performed dry.
NAVAL REACTORS RESEARCH AND DEVELOPMENT
The USA Navy's research and development expanded in eastern Idaho, and by late 1954,
the Nuclear Power Training Unit was established. In 1961, the Naval Administrative Unit set up
shop in Blackfoot. In 1965, the unit moved to a location at Idaho Falls
In the early 1950s work was initiated at the Idaho National Engineering and
Environmental Laboratory (INEEL) to develop reactor prototypes for the USA Navy. The Naval
Reactors Facility, a part of the Bettis Atomic Power Laboratory, was established to support
development of naval nuclear propulsion. The facility was operated by the Westinghouse
Electric Corporation under the direct supervision of the DOE's Office of Naval Reactors. The
facility supports the Naval Nuclear Propulsion Program by carrying out assigned testing,
examination, and spent fuel management activities.
The facility consisted of three naval nuclear reactor prototype plants, the Expended Core
Facility, and various support buildings. The Submarine Thermal Reactor (STR) prototype was
constructed in 1951 and shut down in 1989; the large ship reactor prototype was constructed in
1958 and shut down in 1994; and the submarine reactor plant prototype was constructed in 1965
and shut down in 1995.
The prototypes were used to train sailors for the nuclear navy and for research and
development purposes. The Expended Core Facility, which receives, inspects, and conducts
research on naval nuclear fuel, was constructed in 1958.
The initial power run of the prototype reactor (S1W) as a replacement of the STR for the
first nuclear submarine, the Nautilus, was conducted at the INEEL Laboratory in 1953. The
A1W prototype facility consisted of a dual-pressurized water reactor plant within a portion of the
steel hull designed to replicate the aircraft carrier Enterprise. This facility began operations in
1958 and was the first designed to have two reactors providing power to the propeller shaft of
one ship. The S5G reactor was a prototype pressurized water reactor that operated in either a
forced or natural circulation flow mode. Coolant flow through the reactor was caused by natural
convection rather than pumps. The S5G prototype plant was installed in an actual submarine
hull section capable of simulating the rolling motions of a ship at sea.
The Test Reactor Area (TRA) occupied 102 acres in the southwest portion of the INEEL
laboratory. The TRA was established in the early 1950s with the development of the Materials
Test Reactor (MTR). Two other major reactors were subsequently built at the TRA: the
Engineering Test Reactor (ETR) and the Advanced Test Reactor (ATR). The Engineering Test
Reactor has been inactive since January 1982. The Materials Test Reactor was shut down in
1970.
The major program at the TRA became the Advanced Test Reactor. Since the Advanced
Test Reactor achieved criticality in 1967, it was used almost exclusively by the Department of
Energy's Naval Reactors Program. After almost 30 years of operation, it is projected to remain a
major facility for research, radiation testing, and isotope production into the next century.
The Navy makes shipments of naval spent fuel to INEEL that are necessary to meet
national security requirements to defuel or refuel nuclear powered submarines, surface warships,
or naval prototype or training reactors, or to ensure examination of naval spent fuel from these
sources. The total number of shipments of naval spent fuel to INEEL through 2035 would not
exceed 575 shipments or 55 metric tonnes of spent fuel.
4. COMMERCIAL NUCLEAR SHIPS:
The USA built one single nuclear merchant ship: the Savannah. It is shown in Fig. 4. It
was designed as a national showpiece, and not as an economical merchant vessel. Figure 5
shows the design of its nuclear reactor. For compactness, the steam generators and steam drums
surround the reactor core. This configuration also provides shielding for the crew. It was retired
in 1970.
Nuclear Ice Breakers like the Russian Lenin and the Arktica were a good success, not
requiring refueling in the arctic regions.
The Otto Hahn bulk ore carrier was built by Germany. It operated successfully for ten
years.
The Mutsu was an oceanographic research vessel built in Japan in 1974. Due to a design
flaw causing a radiation leakage from its top radiation shield, it never became fully operational.
The Sturgis MH-1A was a floating nuclear power plant ship (Fig. 6). It was carrying a 45
Megawatts Thermal (MWth) Pressurized water Reactor (PWR) for remote power supplies for the
USA army.
Figure 4. The Savannah, the first USA merchant ship.
5. REACTOR DESIGNS
The nuclear navy benefited the civilian nuclear power program in several ways. It first
demonstrated the feasibility of the Pressurized Water Reactor (PWR) concept, which is being
currently used in the majority of land based power reactors. Second, naval reactors accumulated
a large number of operational experience hours, leading to improvements in the land based
reactors. The highly trained naval operational crews also become of great value to the civilian
nuclear utilities providing them with experienced staffs in the operation and management of the
land based systems.
Land based reactors differ in many way from naval reactors. The power of land based
reactors is in the range of 3,000 MWth or higher. In contrast, a submarine reactor's power is
smaller in the range of the hundreds of MWths. Land based systems use uranium fuel enriched
to the 3-5 percent range. Highly enriched fuel at the 93-97 percent level is used in naval reactors
to provide enough reactivity to override the xenon poison dead time, compactness as well as
provide higher fuel burnup and the possibility for a single fuel loading over the useful service
time of the powered ship.
Figure 5. Loop type of naval reactor design for the nuclear ship Savannah. The reactor core is
surrounded by the heat exchangers and the steam drums. The horizontal steam generator was
replaced by a vertical tube steam generator and an integrated system in future designs.
Figure 6. The MH-1A Sturgis Floating Nuclear Power Plant for remote power applications for
the USA Army.
Table 2 shows the composition of highly enriched fuel used in nuclear propulsion as well
as space reactor designs such as the SAFE-400 and the HOMER-15 designs. Most of the activity
is caused by the presence of U234, which ends up being separated with the U235 component during
the enrichment process. This activity is primarily alpha decay and does not account for any
appreciable dose. Since the fuel is highly purified and there is no material such as fluorine or
oxygen causing any (α, n) reactions in the fuel, the alpha decay of U234 does not cause a neutron
or gamma ray dose. If uranium nitride (UN) is used as fuel, the interaction threshold energy of
nitrogen is well above the alpha emission energies of U234. Most of the dose prior to operation
from the fuel is caused by U235 decay gammas and the spontaneous fission of U238. The total
exposure rate is 19.9 [µRöntgen / hr] of which the gamma dose rate contribution is 15.8 and the
neutron dose rate is 4.1.
Table 2. Composition of highly enriched fuel for naval and space reactors designs.
Isotope
Composition
(percent)
Activity
(Curies)
Decay
Mode
U234
U235
U238
0.74
97.00
2.259
6.1
Pu239
Total
0.001
Alpha decay
Decay gammas
Spontaneous
fissions
Alpha decay
6.5
Exposure
Contribution
[µR/hr]
unappreciable
appreciable
appreciable
unappreciable
19.9
Reactor operators can wait for a 24 hours period; the reactor dead time, on a land based
system for the xenon fission product to decay to a level where they can restart the reactor. A
submarine cannot afford to stay dead in the water for a 24 hour period if the reactor is shutdown,
necessitating highly enriched fuel. A nuclear submarine has the benefit of the ocean as a heat
sink, whereas a land based reactor needs large amounts of water to be available for its safety
cooling circuits
For these reasons, even though the same principle of operation is used for naval and land
based reactor designs, the actual designs differ substantially. Earlier naval reactors used the loop
type circuit for the reactor design as shown in Fig. 5 for the Savannah reactor. There exists a
multitude of naval reactor designs. More modern designs use the Integral circuit type shown in
Fig. 7.
Because of the weight of the power plant and shielding, the reactor and associated steam
generation equipment is located at the center of the ship. Watertight bulkheads isolating the
reactor components surround it. The greater part of the system is housed in a steel containment,
preventing any leakage of steam to the atmosphere in case of an accident. The containment
vessel for the Savannah design consisted of a horizontal cylindrical section of 10.7 meters
diameter, and two hemispherical covers. The height of the containment was 15.2 meters. The
control rod drives are situated in a cupola of 4.27 m in diameter, on top of the containment. The
containment vessel can withstand a pressure of 13 atm. This is the pressure attained in the
maximum credible accident, which is postulated as the rupture of the primary loop and the
subsequent flashing into steam of the entire coolant volume.
The secondary shielding consists of concrete, lead, and polyethylene and is positioned at
the top of the containment. A prestressed concrete wall with a thickness of 122 cm surrounds the
lower section of the containment. This wall rests on a steel cushion. The upper section of the
secondary shielding is 15.2 cm of lead to absorb gamma radiation, and 15.2 cm of polyethylene
to slow down any neutrons. The space between the lead plates is filled with lead wool. The lead
used in the shielding is cast by a special method preventing the formation of voids and
inhomogeneities.
Figure 7. Integral type of naval reactor vessel.
The polyethylene sheets are spaced so as to allow thermal expansion. Thick collison
mats consisting of alternate layers of steel and wood are placed on the sides of the containment.
The effective dose rate at the surface of the secondary sheet does not exceed 5 rem/year.
The containment is airtight. Personnel can remain in it for up to 30 minutes after reactor
shutdown and the radiation level would have fallen to less than 0.2 rem/hr.
The primary shielding is here made of an annular water tank that surrounds the reactor
and a layer of lead attached to the outer surface of the tank, to minimize space. The height of the
tank is 5.2 m, the thickness of the water layer, 84 cm, and the thickness of the lead is 5-10 cm.
The weight of the primary shields is 68.2 tons, and with the water it is 118.2 tons. The
weight of the containment is 227 tons. The secondary shielding weights 1795 tons consisting of:
561 tons of ordinary concrete, 289 tons of lead, 69 tons of polyethylene, and 160 tons of collison
mats. The latter consist of 22 tons of wood and 138 tons of steel.
The shielding complex is optimized to minimize the space used, while providing low
radiation doses to the crew quarters. It is comparatively heavy because of the use of lead and
steel, and is complicated to install.
Figure 7 shows a naval reactor of the Integral circuit type. In this case, the design offers
a substantial degree of inherent safety since the pumps; the steam generators and reactor core are
all contained within the same pressure vessel. Since the primary circulating fluid is contained
within the vessel, any leaking fluid would be contained within the vessel in case of an accident.
This also eliminates the need for extensive piping to circulate the coolant from the core to the
steam generators. In loop type circuits, a possibility exists for pipe rupture or leakage of the
primary coolant pipes. This source of accidents is eliminated in an integral type of a reactor.
5. XENON FORMATION
The fission process generates a multitude of fission products with different yields. Table
3 shows some of these fission products yields resulting from the fission of three fissile isotopes:
Table 3. Fission products yields from thermal 2200 m/sec neutrons,
Isotope
135
53I
135
54Xe
149
61Pm
233
92U
235
92U
0.04750
0.01070
0.00795
0.06390
0.00237
0.01071
i
[nuclei/fission event].
94Pu
239
0.06040
0.01050
0.01210
The most prominent of these fission products from the perspective of reactor control is
It is formed as the result of the decay of 53I135. It is also formed in fission and by the
decay of the Tellurium isotope: 52Te135. This can be visualized as follows:
135
54Xe .
F ission
Te
Te
135
52
I
53
I
135
Xe
135
54
55
Cs
53
135
52
54
53
135
-1
Xe
Cs
135
Ba
135
56
-1
-1
135
54
0
135
55
135
e
I
Xe
135
*
e
e
0
0
( stable )
*
(1)
*
-1
e
0
*
The half lives of the components of this chain are shown in Table 4. The end of the chain
is the stable isotope 56Ba135.
Because 52Te135 decays rapidly with a half life of 11 seconds into 53I135, one can assume
that all 53I135 is produced directly in the fission process.
Denoting I(t) as the atomic density of iodine in [nuclei/cm3], one can write a rate equation
for the iodine as:
dI ( t )
[ rate of form ation of Iodine from fission ]
dt
- [ rate of radioactive transform ations of Iodine ]
dI ( t )
dt
I
f
-
I
I (t )
(2)
where:
I
I
is the fission yield in [nuclei/fission event],
is the thermal fission cross section in [cm-1],
is the decay constant in [sec-1], with λ I =
ln2
T1
, T 1 is the half life.
2
2
Table 4. Half lives of isotopes in the xenon chain.
Half Life, T1/2
11 sec
6.7 hr
9.2 hr
2.3x106 yr
Stable
Isotope
135
52Te
135
53I
135
54Xe
135
55Cs
135
56Ba
A rate equation can also be written for the xenon in the form:
dX ( t )
[ rate of form ation of X enon from fission ]
dt
[ rate of form ation of X e from the transform ation of the Iodine ]
- [ rate of radioactive transform ations of X enon ]
(3)
- [ rate of disappearance of X enon ( X ) through neutron absorptions ],
or :
dX ( t )
dt
X
f
I
I (t) -
X
X (t) -
aX
X (t)
is the thermal microscopic absorption cross section for Xenon equal to 2.65 x 106 [b].
The large value of the absorption cross section of Xe, and its delayed generation from
Iodine, affect the operation of reactors both under equilibrium and after shutdown conditions.
where
aX
6. IODINE AND XENON EQUILIBRIUM CONCENTRATIONS
Under equilibrium conditions, the rate of change of the Iodine as well as the xenon
concentrations is zero:
dI ( t )
dX ( t )
dt
dt
0
This leads to an equilibrium concentration for the Iodine as:
(4)
I
I0
f
(5)
I
The equilibrium concentration for the Xenon will be:
X
X0
f
I
X
I0
(6)
aX
Substituting for the equilibrium concentration of the iodine, we can write:
(
X
X0
I
X
)
f
(7)
aX
7. REACTIVITY EQUIVALENT OF XENON POISONING
Ignoring the effects of neutron leakage, since it has a minor effect on fission product
poisoning, we can use the infinite medium multiplication factors for a poisoned reactor in the
form of the four factor formula:
k
(8)
pf
and for an unpoisoned core as:
k0
We define the reactivity
(9)
pf 0
of the poisoned core as:
k - k0
k
k
f - f0
k
f
1 -
f0
f
In this equation,
f
, is the regeneration factor,
aF
is the fast fission factor,
p is the resonance escape probability,
is the average neutron yield per fission event,
f is the macroscopic fission cross section,
aF is the macroscopic absorption cross section of the fuel,
f is the fuel utilization factor.
(10)
The fuel utilization factor for the unpoisoned core is given by:
aF
f0
aF
(11)
aM
And for the poisoned core it is:
aF
f
aF
(12)
aM
aP
where:
is the moderator's macroscopic absorption coefficient,
aP is the poison's macroscopic absorption coefficients.
aM
From the definition of the reactivity in Eqn. 10, and Eqns. 11 and 12 we can readily get:
aP
aF
(13)
aM
It is convenient to express the reactivity in an alternate form. For the unpoisoned critical core:
1
k0
pf0
aF
p
(14)
aF
aM
From which:
aF
p
aM
(15)
aF
Substituting this value in the expression of the reactivity, and the expression for the regeneration
factor, we get:
1
-
aP
p
(16)
f
For equilibrium Xenon:
(
aP
aX
X0
X
I
X
)
f
aX
aX
Inserting the last equation for the expression for the reactivity we get:
(17)
-
(
X
(
Dividing numerator and denominator by
-
x
aX
(
(
I
)
aX
)
aX
(18)
p
we get:
X
I
x
)
)
(18)’
p
aX
The parameter:
X
0 .7 7 x1 0
13
(20)
aX
at 20 degrees C, and has units of the flux [neutrons/(cm2.sec)].
The expression for the reactivity is written in terms of as:
-
(
X
(
I
)
)
(18)’’
p
For a reactor operating at high flux,
,
and we can write:
-
(
X
I
)
(21)
p
For a reactor fueled with U235,
=2.42, p= =1, the value for
= -
for equilibrium xenon is:
( 0.00237 + 0.06390)
0.06627
2.42
2.42
0.027384
or a negative 2.74 percent.
8. REACTOR DEAD TIME
A unique behavior occurs to the xenon after reactor shutdown. Although its production
ceases, it continues to build up as a result of the decay of its iodine parent. Therefore the
concentration of the xenon increases after shutdown. Since its cross section for neutrons is so
high, it absorbs neutrons and prevents the reactor from being restarted for a period of time
denoted as the reactor dead time. In a land based reactor, since the xenon eventually decays,
after about 24 hours, the reactor can then be restarted. In naval propulsion applications, a naval
vessel cannot be left in the water unable to be restarted, and vulnerable to enemy attack by depth
charges or torpedoes. For this reason, naval reactor cores are provided with enough reactivity to
overcome the xenon negative reactivity after shutdown.
To analyze the behavior, let us rewrite the rate equations for iodine and xenon with
equal to 0 after shutdown:
dI ( t )
-
I
dt
dX ( t )
I
dt
(22)
I (t )
I (t ) -
(23)
X (t)
X
Using Bateman's solution, the iodine and xenon concentrations become:
I (t )
-
I0 e
X (t )
I
X0 e
-
t
(24)
X
t
I
I 0 (e
I
-
t
X
- e
-
(e
-
t
I
(25)
)
X
Substituting for the equilibrium values of X0 and I0 we get:
(
X (t )
X
I
X
)
f
e
-
X
t
I
f
aX
I
X
t
-e
-
t
I
)
(26)
X
The negative reactivity due to xenon poisoning is now a function of time and is given by:
(t )
-
1
aP ( t )
p
-
f
1
aP
X (t )
p
-
aP
X
[
p
(27)
f
X
I
aX
e
-
X
t
I
I
(e
-
X
t
-e
-
I
t
)]
X
Figure 8 shows the negative reactivity resulting from xenon after reactor shutdown. It
reaches a minimum value, which occurs at about 10 hours after shutdown. This post shutdown
reactivity is important in reactors that have operated at a high flux level. If at any time after
shutdown, the positive reactivity available by removing all the control rods is less than the
negative reactivity caused by xenon, the reactor cannot be restarted until the xenon has decayed.
In Fig. 8, at an assumed reactivity reserve of 20 percent, during the time interval from 2.5 hours
60
40
30
16
10
5
2 .5
0
0
N e a g a tiv e R e a c tiv ity fro m X e n o n P o is o n in g
to 35 hours, the reactor cannot be restarted. This period of 35-2.5 = 32.5 hours is designated as
the “Reactor Dead Time.”
-0 .1
X e n o n D e a d tim e
-0 .2
-0 .3
-0 .4
-0 .5
-0 .6
T im e a fte r S h u td o w n , [h o u rs ]
Figure 8. Negative reactivity due to xenon poisoning. Flux = 5x1014 [n/(cm2.sec)].
This reactor dead time is of paramount importance in mobile systems that may be prone
to accidental scrams. This is more important at the end of core lifetime, when the excess
reactivity is limited. For this reason, mobile reactors necessitate the adoption of special design
features, providing the needed excess reactivity to override the negative xenon reactivity, such as
the use of highly enriched cores.
In land based systems such as the CANDU reactor, booster rods of highly enriched U235
are available to override the xenon dead time after shutdown, leading to a higher capacity factor.
Power fluctuations induced to follow demand in any power reactor lead to xenon oscillations
without any reactor shutdown. The changes of xenon concentrations due to load following are
compensated for by adjusting the chemical shim or boron concentration in the coolant, and by
control rods adjustments.
9. NUCLEAR NAVIES
INTRODUCTION
The USA nuclear fleet grew rapidly at the height of the east west cold war in the 1980s.
About one fourth of the submarine fleet carried intercontinental ballistic missiles. These can be
ejected by the use of compressed air while the submarine is totally submerged, with the rocket
engine starting once the missile is above the water surface.
In the Falkland Islands War, a single nuclear British submarine paralyzed the entire
Argentina Naval fleet. It sunk the cruiser “General Belgrano” and forced the Argentine Navy to
not deploy out of port..
During the first and second the Gulf Wars, the USA Navy had unchallenged use of the
oceans and protected 85 percent of the war supplies that were transported by ships.
NAVY CARRIER FORCE
The mission of the aircraft carrier force is to provide a credible, sustainable, independent
forward presence and a conventional deterrence in peace times. In times of crisis, it operates as
the cornerstone of joint and/or allied maritime expeditionary forces. It operates and support air
attacks on enemies, protects friendly forces and engages in sustained independent operations in
times of war. The vital statistics of the nuclear Nimitz Class aircraft carrier are:
Power Plant:
Length:
Beam:
Displacement:
Speed:
Aircraft:
Crew:
Two nuclear reactors, four shafts.
1,092 feet.
134 feet.
97,000 tons at full load.
30 knots, 34.5 miles per hour.
85.
500 officers, 5,000 enlisted.
NUCLEAR SUBMARINE FORCE
The USA submarine force maintains its position as the world’s preeminent submarine
force. It incorporates new and innovative technologies allowing it to maintain dominance
throughout the naval battle space. It incorporates the multiple capabilities of submarines and
develops tactics supporting national objectives through battle space preparation, high seas
control, land battle support as well as strategic deterrence. It also fills the role of a stealthy
signal and intelligence gathering and a full spectrum of special operations and expeditionary
missions. It includes forces of ballistic missiles submarines (SSBN), guided missile submarines
(SSGN), and attack submarines (SSN). The vital statistics of the Ballistic Missile Trident
submarines and the guided missiles submarines are:
Armament, SSBN:
Armament, SSGN:
Power Plant:
Length:
Beam:
Displacement:
Speed:
Crew:
Trident missiles.
154 Tomahawk missiles, 66 Special operation Forces.
One nuclear reactor, one shaft.
560 feet.
42 feet.
18,750 tons, submerged.
20 knots, 23 miles per hour.
15 officers, 140 enlisted.
The statistics for the fast attack Los Angeles class submarines are:
Power Plant:
Length:
Beam:
Displacement:
Speed:
Crew:
One nuclear reactor, one shaft.
360 feet.
33 feet.
6,900 tons, submerged.
25 knots, 28 miles per hour.
12 officers, 121 enlisted.
Figure 9. Christening of a Trident submarine, with two other submarines in different stages of
assembly.
RUSSIAN NAVY
The nuclear Russian navy also reached its peak at the same time as the USA navy. The
first of the TYPHOON class 25,000 ton strategic ballistic missile submarines was launched in
1980 from the Severodvinsk Shipyard on the White Sea. In the same year the first OSCAR class
guided missile was launched. It is capable of firing 24 long range antiship cruise missiles while
remaining submerged. Five shipyards produced seven different classes of submarines. Table 5
shows some of the nuclear powered components of the Russian Navy as it existed then.
Table.5. Principal Components of the Russian Nuclear Navy
Designation
Nuclear Powered Submarines
SSBN
SSBN
SSGN
SSN
Type
Number
Ballistic Missile Submarines, YANKEE,
DELTA, TYPHOON classes.
Ballistic Missile Submarines, HOTEL class
Cruise missile Submarines, ECHO I, II,
CHARLIE I, II.
Torpedo Attack submarines.
62
Guided Missile Cruiser, Kirov Class
1
7
50
60
Nuclear Powered Cruiser
CGN
The Delta IV class is nuclear-powered with two VM-4 pressurized water reactors rated at
180 MWth. There are two turbines, type GT3A-365 rated at 27.5MW. The propulsion system
drives two shafts with seven-bladed fixed-pitch propellers.
CHINESE NAVY
Five hundred years ago the contender for the dominance of the world’s oceans was the
Chinese imperial exploration fleet which was at its peak technologically centuries ahead of its
competitors. A strategic mistake by its emperor was to neglect its sea access with the result of
opening the door to European and then Japanese military intervention and occupation. Being the
world’s second largest importer of petroleum after the USA, China seeks to protect its energy
corridors by sea and free access to Southeast Asia sea lanes beyond the Indochinese Peninsula.
China’s naval fleet as of 2008 had 5 nuclear powered fast attack submarines and one
ballistic missiles submarine carrying 12-16 nuclear tipped missiles with arrange of 3,500 km.
This is in addition to 30 diesel electric submarines with 20 other submersibles under
construction.
The Chinese submarine fleet is expected to exceed the number of USA’s Seventh Fleet
ships in the Pacific Ocean by 2020 with the historic patience and ambition to pursue a long term
strategy of eventually matching and then surpassing the USA’s dominance of the sea.
SURFACE VESSELS
Around 1986, the USA’s nuclear navy reached the level of 134 nuclear submarines, 9
cruisers, and 4 aircraft carriers. By 2001, the number of nuclear carriers increased to 9, as shown
in Table 6 for the Nimitz class of carriers. These aircraft carriers are powered by two nuclear
reactors providing propulsion to 4 shafts each. Typically, the power produced is 280,000 Horse
Power (HP). Since 1 HP is equal to 745.7 Watts, this corresponds to a power of:
280,000 x 745.7 = 208.8 MWth.
Smaller reactors are used in the Enterprise class each of a power of about 26 MWth.
With four propulsion plants each consisting of 2 reactors for a total of 8 reactors corresponding
to 8 steam boilers the total produced power is about 8 x 26 = 208 MWth. Hafnium is used in the
control rods as a neutron absorber. In the newer Nimitz class, reactor sizes are larger at about
105 MWth, all that is needed are two reactors with a total power of 2 x 105 = 210 MWth. Figure
10 shows the Enterprise nuclear aircraft carrier (CVN-65).
Figure 10. The USS nuclear powered aircraft carrier Enterprise CVN-65.
The crew of the Enterprise is about 5,000 sailors with an average age of 25 years, and its
first military operation was in the Cuban missile crisis in 1962. It can top a speed of 30 knots.
Its bridge rises six decks above the flight deck. Its flight deck has an area of 4.47 acres.
It is armed with eight air-wing squadrons, Sea Sparrow missiles, and sophisticated
intelligence gathering and countermeasures equipment. Its mission is to carry military force
within striking range of any point on the planet.
Airplanes land and are catapult launched on two runways. Its air wing has 250 pilots, but
thousands of other sailors plan each flight, maintain the planes and move them using massive
elevators from the hangar deck to the flight deck. The ship is maneuvered so that the head wind
is “sweet” across the deck. Catapults driven with steam from the nuclear reactors fling 30 ton
aircraft to full flight in a space shorter than a football field accelerating it from zero to 165
miles/hr in 2 seconds. Carrier pilots have 350 feet of runway to land. They must come at the
right angle and position to hook one of the four arresting cables or wires. That will bring the
plane to a dead stop. This maneuver has to be completed with engines at full power in case all
the four wires are missed, and the plane has to abort the landing.
Figure 11. The Nuclear Powered Guided Missile Cruiser, KIROV.
Figure 12. The Phalanx radar-guided gun, nicknamed as R2-D2 from the Star-Wars movies, is
used for close-in ship defense. The radar controlled Gatling gun turret shooting tungsten armorpiercing, explosive, or possibly depleted uranium munitions on the USS Missouri, Pearl Harbor,
Hawaii. Photo: M. Ragheb.
The Russian navy's nuclear powered guided missile cruiser KIROV, shown in Fig. 11
from astern, reveals a superstructure massed with radars and electronic sensors, a stern door for
Anti Submarine Warfare (ASW) sonar, and a Ka-25 HORMONE ASW helicopters deck. The
deck is bordered by Gatling guns (Fig.12) using depleted uranium munitions, short range surface
to air missiles and 100 mm dual purpose gun mounts.
Table 6. Principal Components of the USA Nuclear Aircraft Carrier Fleet.
Designation
CVN68
CVN69
CVN70
CVN71
CVN72
CVN73
CVN74
CVN75
CVN76
CVN77
Name
Enterprise
Nimitz
Dwight D. Eisenhower
Carl Vinson
Theodore Roosevelt
Abraham Lincoln
George Washington
John C. Stennis
Harry S. Truman
Ronald Reagan
George W. H. Bush
Class
Enterprise Class, 8 reactors, 4 shafts, 1961.
93,000 tons full load displacement,
1,123 feet length,
257 ft flight deck width,
33 knots speed,
70 aircraft
Nimitz Class, 2 reactors, 4 shafts, 1975.
97,000 tons full load displacement,
1.073 feet flight deck width,
252 ft flight deck width,
32 knots speed,
70 aircraft.
This kind of nuclear powered ship has a displacement of 23,000 tons, larger than any
surface combatant other than an aircraft carrier built since World War II. It is meant as a
multipurpose command ship capable of providing a battle group with enhanced air defense and
surface strike capability. Its primary armament is heavy, highly sophisticated surface to air and
long range antiship cruise missiles. It carries 20 long range cruise missiles, and includes 12
vertical launch tubes for surface to air missiles.
The Russian navy has conducted research and experimentation on new types of
propulsion concepts. It recognized, for instance the advantages of gas turbines for naval
propulsion, and dramatically shifted toward it. Gas turbines offer low weight and volume, in
addition to operational flexibility, reduced manning levels, and ease of maintenance. Even
though gas turbines have been used in surface vessels, it is not clear whether the Brayton gas
turbine cycle has been used instead of the Rankine steam cycle on the nuclear powered ships.
They have built fast reactors, and studied the use of less reactive lead and lead-bismuth alloys
instead of sodium cooling in them. They may also have considered new propulsion concepts
such as dissociating gases and magneto hydrodynamic propulsion.
NUCLEAR CRUISE MISSILE SUBMARINES
Figure 13. Russian cruise missile submarine Project 949A Orel.
The nuclear powered ECHO I and II, and the CHARLIE I and II can fire eight antiship
weapons cruise missiles while remaining submerged at a range of up to 100 kilometers from the
intended target. These cruise missile submarines also carry ASW and antiship torpedoes.
The nuclear cruise missile submarines are meant to operate within range of air bases on
land. Both forces can then launch coordinated attacks against an opponent's naval forces.
Reconnaissance aircraft can the provide target data for submarine launched missiles.
NUCLEAR BALLISTIC MISSILE SUBMARINES
Submarine Launched Ballistic Missiles (SLBMs) on Nuclear Powered Ballistic Missile
Submarines (SSBNs) have been the basis of strategic nuclear forces. Russia had more land
based Intercontinental Ballistic Missiles (ICBMs) than the SLBM forces.
The Russian ICBM and SLBM deployment programs initially centered on the SS-9 and
SS-11 ICBMs and the SS-N-6/YANKEE SLBM/SSBN weapons systems. They later used the
Multiple Independently targetable Reentry Vehicles (MIRVs) SS-N-18 on the DELTA class
nuclear submarines, and the SS-NX-20 on the nuclear TYPHOON class SSBN submarine.
The Russian SLBM force has reached 62 submarines carrying 950 modern SLBMs with a
total of almost 2,000 nuclear warhead reentry vehicles. Russia deployed 30 nuclear SSBNs, and
the 20 tube very large TYPHOON SSBN in the 1980s. These submarines were capable to hit
targets across the globe from their homeports.
Figure 14. The Nuclear Powered Russian Ballistic Missile Submarine Project 667 DRM.
Figure 15. USA Ballistic missile nuclear submarine SSN Ohio.
The 34 deployed YANKEE class nuclear submarines each carried 16 nuclear tipped
missiles. The SS-N-6/YANKEE I weapon system is composed of the liquid propellant SS-N-6
missile in 16 missile tubes launchers on each submarine. One version of the missiles carries a
single Reentry Vehicle (RV) and has an operational range of about 2,400 to 3,000 kilometers.
Another version carries 2 RVs , and has an operational range of about 3,000 kilometers.
The DELTA I and II classes of submarines displaced 11,000 tons submerged and have an
overall length of about 140 meters. These used the SS-N-8 long range, two stages, liquid
propellant on the 12-missile tube DELTA I and the 16 missile tube DELTA II submarines. The
SS-N-8 has a range of about 9,000 kilometers and carries one RV. The SS-N-18 was used on the
16 missile tube DELTA III submarines, and has MIRV capability with a booster range of 6,500
to 8,000 kilometers, depending on the payload configuration. The DELTA III nuclear
submarines could cover most of the globe from the relative security of their home waters with a
range of 7,500 kilometers. Figure 14 shows a DELTA I class SSBN. Figure 15 shows the SSN
Ohio ballistic missile submarine.
The TYPHOON class at a 25,000 tons displacement, twice the size of the DELTA III
with a length of 170 m and 20 tubes carrying the SS-NX-20 missile each with 12 RVs, has even
greater range at 8,300 kms, higher payload , better accuracy and more warheads. Figure 16
shows the known Russian nuclear Ballistic submarines and their missiles systems.
Figure 16. Nuclear Ballistic Missile Submarines and their missiles characteristics.
NUCLEAR ATTACK SUBMARINES
At some time the Russian navy operated about 377 submarines, including 180 nuclear
powered ones, compared to 115 in the USA navy.
The Russian navy operated 220 attack submarines, 60 of them were nuclear powered.
These included designs of the NOVEMBER, ECHO, VICTOR, and ALFA classes. Figure 17
shows the SSN 23 Jimmy Carter Seawolf class attack submarine. Figure 18 shows a VICTORclass attack submarine, characterized by deep diving capability and high speed.
Figure 17. SSN 23, Jimmy Carter nuclear attack submarine, 2005.
ALFA CLASS SUBMARINES
The ALFA class submarine was the fastest submarine in service in any navy. It was a
deep diving, titanium hull submarine with a submerged speed estimated to be over 40 knots. The
titanium hull provided strength for deep diving. It also offered a reduced weight advantage
leading to higher power to weight ratios resulting in higher accelerations. The higher speed
could also be related to some unique propulsion system. The high speeds of Russian attack
submarines were meant to counter the advanced propeller cavitation and pump vibration
reduction technologies in the USA designs, providing them with silent and stealth hiding and
maneuvering.
Figure 18. The Nuclear Powered Russian VICTOR I class Attack Submarine.
The alpha class of Russian submarines used a lead and bismuth alloy cooled fast reactors.
They suffered corrosion on the reactor components and activation through the formation of the
highly toxic Po210 isotope. Refueling needed a steam supply to keep the liquid metal molten
above 257 oF.
Advantages are a high cycle efficiency and that the core can be allowed to cool into a
solid mass with the lead providing adequate radiation shielding. This class of submarines has
been decommissioned.
10. SEAWOLF CLASS SUBMARINES
The Seawolf class of submarines provided stealth, endurance and agility and are the most
heavily armed fast attack submarines in the world.
They provided the USA Navy with undersea weapons platforms that could operate in any
scenario against any threat, with mission and growth capabilities that far exceed Los Angelesclass submarines. The robust design of the Seawolf class enabled these submarines to perform a
wide spectrum of crucial military assignments, from underneath the Arctic icepack to littoral
regions anywhere in the world.
This ship class was capable of entering and remaining in the backyards of potential
adversaries undetected, preparing and shaping the battle space, and, if so directed, striking
rapidly and decisively.
Figure 19. Rollout of the SSN 23 Jimmy Carter attack submarine.
Figure 20. Special features of the SSN 23 Jimmy Carter.
Figure 21. Communications gear on the mast of SSN 23, Jimmy Carter.
Their missions include surveillance, intelligence collection, special warfare, cruise
missile strike, mine warfare, and anti-submarine and anti-surface ship warfare
Table 7. Seawolf class of submarines technical specifications.
Builder
Power plant
Length
Beam
Submerged
Displacement
Speed
Crew
Armaments
Commissioning dates
General Dynamics, Electric Boat Division.
One S6W nuclear reactor, one shaft.
SSN 21 and SSN 22: 353 feet (107.6 meters)
SSN 23: 453 feet (138 meters)
40 feet (12.2 meters)
SSN 21 and SSN 22: 9,138 tons (9,284 metric tons)
SSN 23 12,158 tons (12,353 metric tons)
25+ knots (28+ miles / hour, 46.3+ kilometers / hour)
140: 14 Officers; 126 Enlisted
Tomahawk missiles, MK-48 torpedoes, eight torpedo tubes
Seawolf: July 19, 1997
Connecticut: December11, 1998;
Jimmy Carter: February 19, 2005.
11 JIMMY CARTER SSN 23
The $3.2 billion Jimmy Carter is the third and last of the USA Seawolf class, the huge,
deep-diving subs. With a 50-torpedo payload and eight torpedo tubes, the 453-foot, 12,000-ton
vessel is the biggest of them all. It was delayed to install a 100 foot hull extension.
Figure 22. Comparison of size of SSN 23 Jimmy Carter attack submarine to a Nimitz class
carrier.
It possesses the ability to tap fiber optic undersea cables and eavesdrop on the
communications passing through them.
The Carter was extensively modified for
communications or signal intelligence through the airwaves gathering from its basic design,
given a $923 million hull extension that allows it to house technicians and gear to perform cabletapping, and other secret missions. The Carter's hull, at 453 feet, is 100 feet longer than the other
two subs in the Seawolf class.
Some of the Carter's special abilities: In the extended hull section, the boat can provide
berths for up to 50 special operations troops, such as Navy SEALs. It has an ocean interface that
serves as a sort of hangar bay for smaller Remotely Operated Vehicles (ROVs) and drones. It
has the usual torpedo tubes and Tomahawk cruise missiles, and it will serve as a platform for
researching new technologies useful on submarines.
To listen to fiber-optic transmissions, intelligence operatives must physically place a tap
somewhere along the route. If the stations that receive and transmit the communications along
the lines are on foreign soil or otherwise inaccessible, tapping the line is the only way to
eavesdrop on it.
During the 1970s, a USA submarine placed a tap on an undersea cable along the Soviet
Pacific coast, and subs had to return every few months to pick up the tapes. The mission
ultimately was betrayed by a spy, and the recording device is now at the KGB museum in
Moscow.
Table 8. USS Jimmy Carter technical specifications.
Displacement:
Power plant
Length
Beam
Payload
Weapons
Special Warfare
Sonars
Countermeasures
12,140 tons
Single S6W reactor.
453 feet
40 feet
50 weapons and special operations forces.
Tomahawk land attack missiles, Mark 48 advanced capability
torpedoes, advanced mobile mines, and unmanned undersea
vehicles.
Dry Deck Shelter, Advanced SEAL Delivery System, Ocean
Interface (OI)
Spherical active/passive arrays, wide aperture arrays, TB-16
and TB-29 towed arrays, high frequency sail array, high
frequency and low frequency bow arrays
Internal; reloadable, 32 external non-reloadable
12. OHIO CLASS SUBMARINES
The Ohio class submarine is equipped with the Trident strategic ballistic missile from
Lockheed Martin Missiles and Space. The Trident was built in two versions, Trident I (C4),
which is being phased out, and the larger and longer range Trident II (D5), which entered service
in 1990. The first eight submarines, (SSBN 726 to 733 inclusive) were equipped with Trident I
and the following ten (SSBN 734 to 743) carry the Trident II. Conversion of the four Trident I
submarines remaining after START II (Henry M. Jackson, Alabama, Alaska and Nevada), to
Trident II began in 2000 and is planned to complete in 2008. Lockheed Martin received a
contract in January 2002 for the production of 12 Trident II missiles for the four submarines.
The submarine has the capacity for 24 Trident missile tubes in two rows of 12. The
dimensions of the Trident II missile are length 1,360 cm x diameter 210 cm and the weight is
59,000 kg. The three-stage solid fuel rocket motor is built by ATK (Alliant Techsystems)
Thiokol Propulsion. The US Navy gives the range as “greater than 7,360 km” but this could be
up to 12,000 km depending on the payload mix. Missile guidance is provided by an inertial
navigation system, supported by stellar navigation. Trident II is capable of carrying up to twelve
MIRVs (multiple independent re-entry vehicles), each with a yield of 100 kilotons, although the
SALT treaty limits this number to eight per missile. The circle of equal probability (the radius of
the circle within which half the strikes will impact) is less than 150 m. The Sperry Univac Mark
98 missile control system controls the 24 missiles.
The Ohio class submarine is fitted with four 533mm torpedo tubes with a Mark 118
digital torpedo fire control system. The torpedoes are the Gould Mark 48 torpedoes. The Mark
48 is a heavy weight torpedo with a warhead of 290kg, which has been operational in the US
Navy since 1972. The torpedo can be operated with or without wire guidance and the system has
active and/or passive acoustic homing. Range is up to 50 km at a speed of 40 knots. After launch
the torpedo carries out target search, acquisition and attack procedures delivering to a depth of
3,000ft.
The Ohio class submarine is equipped with eight launchers for the Mk 2 torpedo decoy.
Electronic warfare equipment is the WLR-10 threat warning system and the WLR-8(V)
surveillance receiver from GTE of Massachusetts. The WLR-8(V) uses seven YIG tuned and
vector tuned super heterodyne receivers to operate from 50MHz up to J-band. An acoustic
interception and countermeasures system, AN/WLY-1 from Northrop Grumman, has been
developed to provide the submarine with an automatic response against torpedo attack.
The surface search, navigation and fire control radar is BPS 15A I/J band radar. The
sonar suite includes: IBM BQQ 6 passive search sonar, Raytheon BQS 13, BQS 15 active and
passive high-frequency sonar, BQR 15 passive towed array from Western Electric, and the active
BQR 19 navigation sonar from Raytheon. Kollmorgen Type 152 and Type 82 periscopes are
fitted.
The main machinery is the pressurized water reactor GE PWR S8G with two turbines
providing 60,000 hp and driving a single shaft. The submarine is equipped with a 325 hp
Magnatek auxiliary propulsion motor. The propulsion provides a speed in excess of 18 knots
surfaced and 25 knots submerged.
13. DEEP SUBMERGENCE NUCLEAR SUBMARINE
The NR-1 is a one of a kind nuclear-powered, deep-submergence submarine, capable of
exploring ocean depths to 3,000 feet. Launched on January 25, 1969, and decommissioned on
November 21, 2008, it was one of the oldest nuclear-powered submarines in the nuclear USA
fleet.
This allows access to most of the world’s continental shelves. Its displacement is just
under 400 long tons, which is 1/16th the size of a Los Angeles-class submarine. With her small
size its crew to a mere three officers and eight enlisted men. It has exceptional endurance with a
nuclear propulsion plant allowing uninterrupted bottom operations for up to 30 days. Its
operational period is limited only by the food and air purification supplies that it carries on
board.
Figure 23. The NR-1 deep submergence submarine and its mother ship the SSV Carolyn
Chouest.
The NR-1 was conceived in the 1960s as a deep-ocean, bottom-exploring submarine.
Her turbo-electric drive train provides power to twin 50-horsepower propulsion motors outside
the pressure hull. This results in a mere maximum speed of 3 knots submerged. She is equipped
with four ducted thrusters that enable her to maneuver in every direction, even while hovering
within inches of the ocean floor. She has a conventional rudder and diving planes mounted on
the sail for depth control.
In its nearly 40-year career, the NR-1 was called for countless missions, from searching
for wrecked and sunken naval aircraft to finding debris from the space shuttle Challenger after its
loss in 1986, to tapping into underwater communication cables.
Its highly advanced sonar, unlike the system on an attack submarine, which is directed at
the entire water column, was pointed downward and could detect an “empty soda can buried in
the sand a mile away.”
Some unique features of the NR-1 include having wheels for motion on the ocean floor,
three viewing ports for visual observation, and 29 exterior lights to support 13 television and still
cameras, an object recovery claw, a manipulator arm for various gripping and cutting tools, and a
work basket to hold items recovered from the sea. Numerous protuberances around the ship
include two retractable bottoming wheels mounted with alcohol filled Goodyear truck tires
giving the ship a unique bottom sitting and crawling capability.
The NR-1’s nuclear propulsion plant gives her the ability to operate independently of
surface ships, since it provides ample electrical power for all onboard sensors and life-support
systems and gives the ship essentially unlimited endurance. Due to her small size and relatively
slow speed on the surface, the NR-1 is towed while submerged to and from remote mission
locations by a dedicated support vessel, the SSV Carolyn Chouest (Fig. 23).
14. FUTURE SUBMARINE FORCE: VIRGINIA CLASS
The Virginia class of submarines represents the future nuclear navy force in the USA.
The USA Navy plans on developing the Virginia Class into a fully modular, all-electric
submarine that will accommodate large modules to provide interfaces for future payloads and
sensors. It is a 30 ships class replacing the Los Angeles Class SSNs, possessing the stealth of the
Seawolf Class of submarines but at a 30 percent lower total cost. It has mission reconfigurable
modules capabilities. It is equipped with Unmanned Undersea Vehicles (UUVs) and improved
sensors and communication systems. It is characterized with improved habitability, and is
equipped with advanced strike munitions and deployable networked sensors.
The main propulsion units are the ninth generation GE Pressurized Water Reactor S9G,
designed to last as long as the submarine, two turbine engines with one shaft and a United
Defense pump jet propulser, providing 29.84 MW. The speed is 25+ knots dived.
Figure 24. Characteristics of the Virginia class of the nuclear all-electric submarines.
Figure 25. Cutout of Virginia class submarine. Note the innovative jet pump propulsion system
at left. Source: General Dynamics.
Its principal features are:
1. An all electrical ship.
2. Enhanced stealth.
3. Modular isolated decks.
4. Open system architecture.
5. Modular masts.
6. Structurally integrated enclosures.
7. Mission reconfigurable torpedo room.
8. Enhanced special warfare capabilities.
9. Enhanced Littoral performance.
The Technical Specifications of the Virginia Class submarine are listed in Table 9.
Table 9. Technical Specifications of the Virginia Class of Submarines.
Power Plant
Displacement
Length
Draft
Beam
Speed
Horizontal tubes
Vertical tubes
Weapon systems
Single S9G PWR
Single shaft with pump jet propulsion
One secondary propulsion submerged motor
7,800 tons, submerged
277 ft
32 ft
34 ft
25+ knots, submerged
Four 21 inches torpedo tubes
12 Vertical Launch System Tubes
39, including:
Vertical Launch System Tomahawk Cruise Missiles
Mk 48 ADCAP Heavy weight torpedoes
Advanced Mobile Mines
Unmanned Undersea Vehicles
Special warfare
Sonars
Counter measures
Crew
Dry Deck Shelter
Spherical active/passive arrays
Light Weight Wide Aperture Arrays
TB-16, TB-29 and future towed arrays
High frequency chin and sail arrays
1 internal launcher
14 external launchers
113 officers and men
It is designed for mine avoidance, special operations forces delivery and recovery. It uses
non acoustic sensors, advanced tactical communications and non acoustic stealth. In the future it
will be equipped with conformal sonar arrays. Conformal sonar arrays seek to provide an
optimally sensor coated submarine with improved stealth at a lower total ownership cost. New
technology called Conformal Acoustic Velocity Sonar (CAVES) will replace the existing Wide
Aperture Array technology and will be implemented starting in early units of the Virginia class.
High Frequency Sonar will play more important role in future submarine missions as
operations in the littorals require detailed information about the undersea environment to support
missions requiring high quality bathymetry, precision navigation, mine detection or ice
avoidance. Advanced High Frequency Sonar systems are under development and testing that
will provide submarines unparalleled information about the undersea environment. This
technology will be expanded to allow conformal sonar arrays on other parts of the ship that will
create new opportunities for use of bow and sail structure volumes while improving sonar sensor
performance.
15. S9G NINTH GENERATION REACTOR DESIGN
The S9G Next Generation Reactor and associated components will have increased energy
density. The core that is under development for the New Attack Submarine is expected to last
the life of the ship. The design goals include eliminating the need for a refueling, will reduce life
cycle costs, cut down the radiation exposure of shipyard workers, and lessen the amount of
radioactive waste generated. This is possible because of many developments such as use of
advanced computers to perform three-dimensional nuclear, thermal, and structural calculations;
further exploitation of the modified fuel process; and better understanding of various reactor
technologies which permits more highly optimized designs. Performance improvements are
gained through advances in such areas as thermal hydraulics and structural mechanics, and by
optimizing reactor-to-systems interfaces.
The new reactor which will have increased energy density, and new plant components,
such as a new concept steam generator, with improved corrosion resistance and reduced lifecycle costs. The new steam generators will also allow greater plant design flexibility and
decreased construction costs due to smaller size, spatial orientation, and improved heat transfer
efficiency which reduces coolant flow requirements. A new concept steam generator would
alleviate the corrosion concerns encountered in existing designs of steam generators, while
reducing component size and weight and providing greater flexibility in overall arrangement.
16. NUCLEAR ICE BREAKERS
INTRODUCTION
Nuclear-powered icebreakers were constructed by Russia for the purpose of increasing
the shipping along the northern coast of Siberia, in ocean waters covered by ice for long periods
of time and river shipping lanes. The nuclear powered icebreakers have far more power than
their diesel powered counterparts, and for extended time periods. During the winter, the ice
along the northern Russian sea way varies in thickness from 1.2 - 2 meters. The ice in the central
parts of the Polar Sea, is 2.5 meters thick on average. Nuclear-powered icebreakers can break
this ice at speeds up to 10 knots. In ice free waters the maximum speed of the nuclear powered
icebreakers is 21 knots.
In 1988 the NS Sevmorpu was commissioned in Russia to serve the northern Siberian
ports. It is a 61,900 metric tonnes, 260 m long and is powered by the KLT-40 reactor design,
delivering 32.5 propeller MW from the 135 MWth reactor.
APPLICATIONS
Russia operated at some time up to eight nuclear powered civilian vessels divided into
seven icebreakers and one nuclear-powered container ship. These made up the world's largest
civilian fleet of nuclear-powered ships. The vessels were operated by Murmansk Shipping
Company (MSC), but were owned by the Russian state. The servicing base Atomflot is situated
near Murmansk, 2 km north of the Rosta district.
Figure 26. Nuclear icebreaker Arktika.
Figure 27. Schematic of Russian Nuclear icebreaker Arktika showing emplacement of nuclear
reactor at its center.
Icebreakers facilitated ores transportation from Norilsk in Siberia to the nickel foundries
on the Kola Peninsula, a journey of about 3,000 kms.
Since 1989 the nuclear icebreakers have been used to transport wealthy Western tourists
to visit the North Pole. A three week long trip costs $ 25,000.
The icebreaker Lenin, launched in 1957 was the world's first civilian vessel to be
propelled by nuclear power. It was commissioned in 1959 and retired from service in 1989.
Eight other civilian nuclear-powered vessels were built: five of the Arktika class, two river
icebreakers and one container ship. The nuclear icebreaker Yamal, commissioned in 1993, is the
most recent nuclear-powered vessel added to the fleet as shown in Table 10.
Table 10. Russian civilian ice breakers operated by the Murmansk Shipping Company.
Ice Breaker
Lenin
Arktika
Sibir
Rossiya
Sevmorput
Taimyr
Sovyetskiy
Soyuz
Vaigach
Jamal
Launch /
Decommissioning Dates
1959 / 1989
1975
1977
1985
1988
1989
1990
1990
1993
Class or Type
Icebreaker
Arktika
Arktika
Arktika
Container ship
River icebreaker
Arktika
Soyuz
River icebreaker
Arctika
REACTOR TYPES FOR ICEBREAKERS
The nuclear icebreakers are powered by pressurized water reactors of the KLT-40 type.
The reactor contains fuel enriched to 30-40 percent in U235. By comparison, nuclear power
plants use fuel enriched to only 3-5 percent. Weapons grade uranium is enriched to over 90
percent. American submarine reactors are reported to use up to 97.3 percent enriched U235. The
irradiated fuel in test reactors contains about 32 percent of the original U235, implying a discharge
enrichment of 97.3 x 0.32 = 31.13 percent enrichment.
Under normal operating conditions, the nuclear icebreakers are only refueled every three
to four years. These refueling operations are carried out at the Atomflot service base.
Replacement of fuel assemblies takes approximately 1 1/2 months.
For each of the reactor cores in the nuclear icebreakers, there are four steam generators
that supply the turbines with steam. The third cooling circuit contains sea water that condenses
and cools down the steam after it has run through the turbines. The icebreaker reactors' cooling
system is especially designed for low temperature Arctic sea water.
17. DECOMMISSIONING AND DEFUELING
Navy nuclear ships are decommissioned and defueled at the end of their useful lifetime,
when the cost of continued operation is not justified by their military capability, or when the ship
is no longer needed. The Navy faces the necessity of downsizing the fleet to an extent that was
not envisioned in the 1980’s before the end of the Cold War. Most of the nuclear-powered
cruisers will be removed from service, and some Los Angeles Class submarines are scheduled
for removal from service. Eventually, the Navy will also need to decommission Ohio Class
submarines.
Nuclear ships are defueled during inactivation and prior to transfer of the crew. The
defueling process removes the nuclear fuel from the reactor pressure vessel and consequently
removes most of the radioactivity from the reactor plant. Defueling is an operation routinely
accomplished using established processes at shipyards used to perform reactor servicing work.
After a nuclear-powered ship no longer has sufficient military value to justify continuing
to maintain the ship or the ship is no longer needed, the ship can be: (1) placed in protective
storage for an extended period followed by permanent disposal or recycling; or (2) prepared for
permanent disposal or recycling. The preferred alternative is land burial of the entire defueled
reactor compartment at the Department of Energy Low Level Waste Burial Grounds at Hanford,
Washington.
A ship can be placed in floating protective storage for an indefinite period. Nuclearpowered ships can also be placed into storage for a long time without risk to the environment.
The ship would be maintained in floating storage. About every 15 years each ship would have to
be taken out of the water for an inspection and repainting of the hull to assure continued safe
waterborne storage. However, this protective storage does not provide a permanent solution for
disposal of the reactor compartments from these nuclear-powered ships. Thus, this alternative
does not provide permanent disposal.
Unlike the low-level radioactive material in defueled reactor plants, the Nuclear Waste
Poficy Act of 1982, as amended, requires disposal of spent fuel in a deep geological repository.
The Hanford Site is used for disposal of radioactive waste from DOE operations. The pre
Los Angeles Class submarine reactor compartments are placed at the Hanford Site Low Level
Burial Grounds for disposal, at the 218-E-12B burial ground in the 200 East area. The land
required for the burial of approximately 100 reactor compartments from the cruisers, Los
Angeles, and Ohio Class submarines would be approximately 4 hectares or 10 acres..
An estimated cost for land burial of the reactor compartments is $10.2 million for each
Los Angeles Class submarine reactor compartment, $12.8 million for each Ohio Class submarine
reactor compartment, and $40 million for each cruiser reactor compartment.
The estimated total Shipyard occupational radiation exposure to prepare the reactor
compartment disposal packages is 13 rem generating a risk of approximately 0.005 additional
latent cancer fatalities for each Los Angeles Class submarine package, 14 rem or a risk of
approximately 0.006 additional latent cancer fatalities for each Ohio Class submarine package
and 25 rem or a risk of approximately 0.01 additional latent cancer fatalities for each cruiser
package.
18. ACCIDENTS OCCURRENCES
INTRODUCTION
Naval vessels are built in a highly sturdy fashion to withstand combat conditions and
their crews are highly professional and well trained. Accordingly, accidents occurrences have
been rare, but reporting about them is sketchy even though there is a need to learn from their
experience to avoid their future occurrence. The Naval Reactors office at the USA Department
of Energy (USDOE) defines an “accident” as an event in which a person is exposed to radiation
above the prescribed safe federal limits.
The most notable accidents for the USA Navy were the loss of the Thresher and the
Scorpion nuclear submarines. The discovery of the Titanic wreck was a spinoff of the
technology developed for investigating these accidents at great water depths.
USS THRESHER, SSN-593, ACCIDENT, 1963
The USS Thresher of the Permit class attack submarine was powered with a
Westinghouse S5W nuclear reactor, with a displacement of 4,300 metric tonnes, a length of 85
meters, and a maximum speed of 30 knots. The crew of 129 comprised 12 officers, 96 enlisted
men, 4 shipyard officers, and 17 civilian specialists.
On April 9, 1963 the USS Thresher, accompanied by the submarine rescue ship USS
Skylark (ASR-20), sailed out of Portsmouth, New Hampshire for a planned 2 days of deep
diving test trials.
On the morning of April 10, 1963 at 8:53 am, the Thresher dived contacting the Skylark
at every 49 meters of its dive. As it neared its test depth, around 9:10 am it did not respond to
the Skylark’s communications. The Skylark’s queries were answered by the ominous sound of
compartments collapsing. Surface observers realized that the Thresher was lost when their sonar
operations heard the sound of compressed air for 20-30 seconds. The Skylark reported to
headquarters that it lost contact with the Thresher at 9:17 am. The accident sequence lasted
about 7 minutes.
The possible causes of the accident were surmised to be:
1. Water leaking from damaged pipes inside the pressure hull,
2. The pressure hull disintegrating when the submarine approached its maximum diving depth of
3,000 feet or (304 x 3,000) / 1,000 = 912 meters. (1,000 feet = 304 meters),
3. The submarine dived below its maximum diving depth due to crew error in an area with a
depth of 8,400 feet or (304 x 8,400) / 1,000 = 2,560 meters.
An extensive underwater search using the deep diving bathyscaphe Trieste located the
Thresher on the sea floor broken into 6 major sections. The debris field covered an area of
134,000 m2 or 160,000 square yards. A possible human error could be related to the initial
testing being undertaken at a relatively high depth location.
USS SCORPION, SSN-589, ACCIDENT, 1968
The USS Scorpion was a 3,500 ton Skipjack class nuclear-powered attack submarine
built at Groton, Connecticut. It was commissioned in July 1960 and assigned to the Atlantic
Fleet. The Scorpion was assigned to a Mediterranean cruise in February 1968. The following
May, while homeward bound from that tour, she was lost with her entire crew some 400 miles
southwest of the Azores Island.
The Scorpion was designed primarily for anti submarine warfare against the USSR
nuclear submarine fleet and it carried special teams of Russian-speaking linguists to eavesdrop
on transmissions by the USSR Navy and other military units.
On May 17, 1968, led by Cmdr. Francis Slattery, the Scorpion had just completed a three
month deployment to the Mediterranean Sea with the USA 6th Fleet and was on its way home to
Norfolk, Virginia. Vice Adm. Arnold Schade, commander of the Atlantic Submarine Force in
Norfolk, had a new mission for the Scorpion. The submarine was ordered to head at high speed
toward the Canary Islands, 1,500 miles away off the east coast of Africa, to gather intelligence
on a group of USSR ships lurking in the eastern Atlantic southwest of the Azores island chain.
The Soviet ships there included an Echo-II class nuclear submarine designed to attack aircraft
carriers but also armed with anti-submarine torpedoes.
In late October 1968, the remains of the Scorpion were found on the sea floor over
10,000 feet below the surface by a towed deep-submergence vehicle deployed from the USNS
submersible craft Mizar (T-AGOR-11).
Photographs showed that her hull had suffered fatal damage while she was running
submerged and that even more severe damage occurred as she sank. The cause of the initial
damage continues to generate controversy decades later and may have been a casualty of the
Cold War.
On May 17, 1968, the USS Scorpion had received a top secret message shortly before
midnight to change course and head for the Canary Islands, where a collection of USSR ships
had caught the Navy's attention. Thirty three minutes later, the Scorpion surfaced at the USA
submarine base at Rota, Spain, to transfer two crewmen ashore via a Navy tug. The men had
emergency leave orders, one for a family matter and the other for medical reasons. The
submarine sank five days later on May 22, 1968.
More than five months later, the Scorpion's wreckage was found on the ocean floor, two
miles deep in the Atlantic. All 99 men aboard were lost.
The USA Navy's initial position was that the Scorpion sank because of a malfunction
while returning to its home port of Norfolk, Virginia. While the precise cause of the loss
remained undetermined, there was no information to support the theory that the submarine's loss
resulted from hostile action of any involvement by a USSR ship or submarine.
Another opinion suggested that the Scorpion was at the center of a web of intelligence
gathering and surveillance and a possible Cold War military activity that resulted in an alleged
agreement by both the USA and the former USSR to cover up the full accounting of what
happened.
A scenario dramatically different from the official Navy version was reported alleging
that the Scorpion was not on a routine crossing of the Atlantic, but had been diverted to a topsecret mission to spy on a group of Soviet ships, including a nuclear submarine. Although the
Navy's official explanation was of a mechanical malfunction, this countered an earlier conclusion
by a panel of senior Navy officials that the Scorpion was sunk by a torpedo. The panel
concluded it was one of the Scorpion's own torpedoes that went errant. Experts still disagree
about whether it could have been a USSR torpedo.
Figure 28. Launch of the USS Scorpion.
An allegation was that even though the Scorpion believed it was operating in secret,
Navy warrant officer John Walker, the Navy's most notorious spy, had communicated to the
USSR the codes they needed to track the USA submarine in the hours before it sank. The USSR
had the ability to monitor all electronic transmissions to the Scorpion, including the encrypted
orders sending it on its intelligence gathering mission.
Russian Navy admirals said that senior Navy officials in both the USA and the USSR
agreed to never disclose details of the Scorpion incident and the loss of a Soviet missile sub in
the Pacific two months earlier in 1968.
Two months before the Scorpion sank, a Soviet missile sub known as the K-129 sank
thousands of miles away, in the Pacific Ocean, also under mysterious conditions. There have
been assertions by Russian submarine veterans over the years that the K-129 sank after an
alleged collision with a USA attack submarine that allegedly had been shadowing it. USA
military officials insisted the Golf-class submarine went down with its 98 man crew after an
internal explosion, based on analysis of the sounds of the sinking captured on Navy
hydrophones.
Retired Capt. Peter Hutchhausen was the USA Naval attaché in Moscow in the late
1980s, two decades after both incidents. He reported that he had several terse but pointed
conversations with counterpart Soviet admirals about the two sinkings of the Scorpion and the KK-129. One encounter was in June 1987 with Admiral Pitr Navoytsev, first deputy chief for
operations of the Soviet Navy. When he asked Navoytsev about the Scorpion, Capt.
Hutchhausen recalls his response: “Captain, you are very young and inexperienced, but you will
learn that there are some things both sides have agreed not to address, and one is that event and
our K-129 loss, for similar reasons.” In another discussion in October 1989, Capt. Huchthausen
said Vice Adm. B.M. Kamarov told him that a secret agreement had been reached between the
USA and USSR in which both sides agreed not to press the other government on the loss of their
submarines in 1968. The motivation, Capt. Huchthausen said, was to preserve the thaw in
superpower relations.
A senior admiral in the Pentagon at the time of the Scorpion sinking said that USA
intelligence agencies feared the submarine was headed into possible danger, based on intercepted
Soviet naval communications in the Atlantic Ocean.
There was some communications analysis that the Scorpion had been detected by the
group she had been shadowing and conceivably they had trailed her. There were some
speculations that not only did they track her but attacked her as a tit-for-tat for the K-129 sinking.
A further suggestion was that it was lured into a trap and ambushed. However, the intelligence
of USSR hostility has never been confirmed.
The Navy mounted a secret search for the submarine within 24 hours of its sinking. The
search was highly classified. The rest of the Navy, and even a Navy Court of Inquiry that
investigated the sinking later in 1968, were never told about it.
The Court of Inquiry that probed the loss of the Scorpion in the summer and fall of 1968
described the Soviet presence as an undefined “hydro-acoustic” research operation involving two
research vessels and a submarine rescue ship among others, implying the Soviets were merely
engaging in research on oceanographic studies of sound effects in the ocean rather than a
military mission. Pentagon officials had been concerned that the USSR was developing a way to
support warships and submarines at sea without requiring access to foreign seaports for supplies.
What is known is that 15 hours after sending its final message, the Scorpion exploded at
6:44 pm on May 22, 1968, and sank in more than 2 miles of water depth about 400 miles
southwest of the Azores. The Navy said it could not identify the “certain cause” of the loss of
the Scorpion.
In late 1993, the Navy declassified most of the Court of Inquiry's 1968 conclusions that it
had earlier classified. Headed by retired Vice Adm. Bernard Austin, the court had concluded
that the best evidence pointed to an errant Scorpion own torpedo that circled around and
exploded against the hull of the sub. The court's conclusion stemmed in part from records
showing that the Scorpion has had a similar occurrence in 1967 with an unarmed training
torpedo that suddenly started up and had to be jettisoned.
In its final 1,354-page report, the Court of Inquiry rejected two alternative theories for the
loss: the contention by that an unspecified mechanical problem had set off a chain of events
leading to massive flooding inside the submarine, and a scenario that an explosion inside the
submarine touched off the sinking. The court also concluded that it was "improbable" the
Scorpion sank as the result of "enemy action."
In 1970, a different Navy panel completed another classified report that disavowed the
Court of Inquiry's conclusion. Instead of an accidental torpedo strike, the new group suggested a
mechanical failure caused an irreparable leak that flooded the submarine. That report said the
bulk of the evidence suggested an internal explosion in the submarine’s massive electrical
battery caused the sub to flood and sink.
Two senior Navy officials involved in the initial Scorpion probe in the summer of 1968
suggested that the Court of Inquiry conclusion of an accidental torpedo strike remains the most
realistic scenario because of the key acoustic recordings of the sinking. Underwater recordings
retrieved from three locations in the Atlantic, the Canary Islands and two sites near
Newfoundland, captured a single sharp noise followed by 91 seconds of silence, then a rapid
series of sounds corresponding to the overall collapse of the submarine's various compartments
and tanks. There was no way one can have the hull implode and then have 91 seconds of silence
while the rest of the hull decides to try and hang itself together.
Retired Adm. Bernard Clarey, who in 1968 was the Navy's senior submariner, dismissed
the battery explosion theory asserting that such a mishap could not have generated the blast and
acoustic energy captured on the hydrophone recordings.
While several retired submariners over the years have speculated the Scorpion was
ambushed and sunk by a Soviet submarine, no conclusive proof of a deliberate attack has
appeared. The Navy concluded in 1968 probe there was “no evidence of any Soviet preparations
for hostilities or a crisis situation as would be expected in the event of a premeditated attack on
Scorpion.”
The Court of Inquiry report was silent on whether an inadvertent clash may have resulted
in the sinking. A Navy spokesperson said the Court of Inquiry had found the Scorpion was 200
miles away from the Soviet ships at the time it sank.
JOHN S. STENNIS, CVN-74 LOCA ACCIDENT, 1999
On November 30, 1999 the nuclear aircraft carrier CVN-74 John S. Stennis ran aground
in a shallow area adjacent to its turning basin as it attempted to maneuver off the California coast
near Naval Air Station North Island, San Diego. This resulted into clogging by silt of the inlet
coolant pipes to its two reactors and causing what would amount to a loss of cooling accident for
a period of 45 minutes. One reactor was shut down by the automatic control system and the
second was left running at low power to provide energy to the vessel and eventually taken offline
by the operators until an alternate cooling supply was provided. The vessel was possibly
lightened of its water and fuel supplies and towed by tugboata to its pier at high tide. The
cleanup cost about $2 million.
SAN FRANSISCO UNDERWATER COLLISION, 2005
A January 8, 2005 incident occurred to the USS San Francisco nuclear submarine which
sustained structural damage that shredded its bow and destroyed a water filled fiberglass sonar
dome and forward ballast tanks when it hit in a glancing blow an underwater mountain 525 feet
underwater that was not on its navigational charts.
Satellites images showed the presence of the mountain but were not incorporated into the
navigational charts. The submarine was travelling at 30 knots when the accident occurred. The
accident caused the death of one sailor and injured 60 others. The submarine crew took
emergency measures to blast to the surface and keep the vessel afloat. An air blower was run for
30 hours to limit water seepage from holes in the forward ballast tanks keeping the vessel from
sinking too low to maneuver.
The hull of a submarine is composed of two parts made of high strength steel such as
HY-80 for the LA class submarines. The inner hull, that is much thicker and stronger than the
outer hull and encloses the crew’s living quarters and working spaces, held firm. The high yield
steel can withstand pressure at depths greater than 800 feet and has a seamless rubberlike
substance molded onto its surface. The ballast tanks are positioned between the two hulls. Two
doors that shutter the torpedo hatches held tight and did not flood. The nuclear reactor was
unaffected and powered the vessel back 360 miles northeast to its port at Guam.
The nose cone that is constructed of a composite material enabling sound to pass through
it to a sonar sphere with active and passive sonar, was shattered. The sonar sphere is covered
with hydrophones mounted on its surface and is isolated from sounds generated by the submarine
by a baffle. In addition to the spherical array, the Virginia class of submarines is equipped with a
chin, sail, three side mounted arrays on each side and a towed array that eliminates much of the
blind area behind the submarine.
Figure 29. USS San Francisco accident, January 8, 2005. Damage from the glancing collision to
the bow dome and to the double hull structure can be observed. A bulge over the hull can also
be noticed.
NERPA, AKULA CLASS FIRE, 2008
An accident occurred on the Nerpa, an Akula Class Russian nuclear attack submarine on
sea trials in the Pacific Ocean that was planned to be leased to the Indian Navy on November 8,
2008. The event claimed twenty deaths and 21 injuries to people who were not able to use the
portable breathing gear issued to Russian submarine crews. The deaths were caused by the
inhalation of the freon toxic gas used as a fire suppressant in the vessel’s fire extinguishing
system that went off unexpectedly. Most of the injured were civilian workers from the Amur
Ship Building Enterprise shipyard that built the submarine. Seventeen victims were civilian
employees and three were sailors. Reportedly, 208 people or about 3 times the size of the usual
crew were on board the submarine during its testing.
Figure 30. Akula Class Russian nuclear submarine with its tail sonar gear.
USS HOUSTON COOLANT LEAK, 2008
In 2008, it was reported that the nuclear submarine USS Houston had a coolant leak.
This was the first coolant leakage of its kind, and because of its small magnitude; it went
undetected for two years.
HMS VANGUARD, LE TRIOMPHANT COLLISION, 2009
While travelling at low speed, the ballistic missile submarine HMS Vanguard sustained
dents and scratches on its hull when it collided in the Atlantic with the French ballistic missile
submarine Le Triomphant in early 2009. The latter incurred damage to its sonar dome located
under its bow. The sophisticated sonar equipment failed to detect the presence of the other
submarine directly ahead of it.
Figure 31. British nuclear submarine HMS Vanguard to the left, and French Le Triomphant
(The Triumphant) to the right collided in the Atlantic in 2009.
The UK possesses four ballistic missiles submarines, as do the French, the USA has 14,
the Russians 15, and the Chinese three. The 173 meter or 567 feet long Dimitry Donskoy is the
world's largest strategic submarine with twice the displacement of the Kursk, which sank in the
Barents Sea with 118 sailors in 2000. The hull of the Vanguard is as tall as a four story building
and roughly 150 meters or 492 feet in length, and carries 16 ballistic missiles armed with nuclear
warheads with a combined power more than about 6 Mt of TNT equivalent.
The methods used to detect submarines do not function reliably except for the passive
and active sonars. Special magnetic detectors have been developed to detect the imprints a large
steel vessel makes in the Earth's magnetic field, but many external factors can interfere with the
devices. Infrared receivers can detect the heat wake generated by a nuclear reactor, but they also
mistakenly identify the water being churned up behind a freighter as a submarine. Laser
scanning beams cannot penetrate far enough beneath the ocean surface. Bioluminescence
detectors detect the light emitted by microbes agitated by a submarine's propellers, but the same
microbes also emit light for other reasons. The radioactive wake from neutron activation of the
sodium in sea water salt is hard to detect.
Active sonar transmits “ping” noises into the water like whales, and the resulting echo
enables the sonar device to compute the location and size of a submarine. However, sound
travels far underwater, and a submarine that transmits sound will be revealing its location to a
potential adversary. That is why strategic nuclear submarines use passive sonar which a system
of highly sensitive hydrophones that uses computers to interpret underwater sounds. A problem
is that submarines are extremely quiet; thanks to the use of special propellers and sound insulated
engines, and their commanders usually driving them at no more than a walking pace making
“less noise than a crab.”
In addition, the ocean is a structured labyrinth for submarine ommanders. Layers of
water with different salinity levels mimic horizontal ramps and the solid ocean floor, because the
layers between them reflect and refract sound waves. Warm currents build vertical walls in the
same way. This creates safe spots in the middle of the ocean into which strategic submarine
commanders like to lurk and embed their vessels in, as well as to follow hidden paths that tend to
be used by all submarines.
The UK and the USA coordinate the positions of their submarines with France expected
to join the NATO military command structure. That leaves Russia and China out.
HARTFORD AND NEW ORLEANS ACCIDENT, 2009
In the morning of March 20, 2009, the 2,899 ton nuclear submarine USS Hartford as part
of the USA 5th fleet, was transiting into the Persian Gulf through the Hormuz Straits. It was
accompanying an amphibious surface ship, the USS New Orleans, LPD-18, which was making
her first extended deployment. The Hartford was submerged but near the surface at the time of
the collision.
The two ships collided, and the submarine Hartford rolled 85 degrees to starboard. The
impact and rolling caused injuries to 15 Sailors onboard. The bow planes and sail of the
submerged Hartford ripped into the hull of the New Orleans.
The collision punched a 16-by-18 foot hole in the fuel tanks of the New Orleans. Two
interior ballast tanks were also damaged. The New Orleans lost about 25,000 gallons of diesel
fuel, which rapidly dissipated in the ocean and could not be tracked after a few days. There were
no injuries to the New Orleans crew of 360 or the embarked unit of 700 USA Marines.
The nuclear powered submarine Hartford was severely damaged as its sail was torn from
its mountings to the vessel’s pressure hull. The submarine’s communication masts and periscope
were warped and became inoperable. The watertight integrity of the pressure hull became
suspect, yet the Hartford transited on its own power on the surface to Bahrain, where it tied up to
a military pier. The nuclear power plant was unaffected by the collision.
The Hartford ran aground in 2003 near La Maddalena, Italy damaging the bottom and
rudder. Repairs involved the installment of equipment that was cannibalized from a
decommissioned submarine.
Figure 32. The collision of the Hartford with the New Orleans on March 20, 2009 caused
damage to its communication gear and bent its sail.
Table 11. Nuclear submarine accidents since 1968.
Accident
USA Navy submarine
Scorpion sinks with 99 men
aboard.
French submarine, The
Eurydice sinks with 57 crew
members
Soviet November Class
nuclear attack submarine sinks
with 88 crew members
Explosion on a Russian
submarine sends up the reactor
lid 100 meters, claiming a
maintenance crew of 10
people
Soviet Mike Class submarine
develops a fire with a loss of
Location
East of Norfolk, Virginia
Date
May-June 1968
Off Saint Tropez,
Mediterranean Sea
March 4, 1970
Atlantic Ocean, off Spain
April 12, 1970
Chazma Bay on the Paciific
coast by Vladivostock
Off northern Norway
August 10, 1985
April 7, 1989
42 lives
Toxic fuel leaked from a
ballistic missile and poisoned
several Russian serice men
Russian Oscar-II Class
submarine Kursk sinks with
118 crew members after a
possible collision and two
explosions onboard
USA Navy 360 feet
submarine, The Greenville
sinks a Japanese fishing
trawler after colliding with it
in a resurfacing training
maneuver, killing 9 sailors
aboard the boat
Russian K-139 submarine
sank while being towed to a
shipyard with 9 crew members
aboard
USA San Francisco runs into
undocumented underground
mountain, killing one crew
member
Fire on board the Viktor-3
class Russian Navy submarine
St. Daniel of Moscow kills 2
crew members
British submarine the Tireless
during an exercise has 2
soldiers killed and 1 injured
The Nerpa, Akula class
Russian submarine fire causes
the death of 20 people and
injuring 21 while on sea trials
The Hartford nuclear
submarine while submerged
but near the surface collides
with the surface ship USS
New Orleans. The collision
caused 15 injuries on the
Hartford.
Russia’a far east
June 16, 2000
Barents Sea
August 12, 2000
Pacific Ocean off Pearl
Harbor, Hawaii
February 9, 2001
August 28, 2003
Off Guam, Pacific Ocean
Moored near Finnish border
January 2005
September 6, 2006
Arctic Ocean
March 21, 2007
Pacific Ocean
November 8, 2008
Strait of Hormuz
March 20, 2009
ALL ELECTRIC PROPULSION AND STEALTH SHIPS
Three trends are shaping the future of naval ship technology: the all electrical ship,
stealth technology and littoral vessels.
Littoral Combat Ships are designed to operate closer to the coastlines than existing
vessels such as destroyers. Their mission is signal intelligence gathering, insertion of special
forces, mine clearance, submarine hunting and humanitarian relief.
The all-electric ship propulsion concept was adopted from the propulsion system of
cruise ships for the future surface combatant power source. It would encompass new weapon
systems such as modern electromagnetic rail-guns and lasers under development.
To store large amounts of energy, flywheels, large capacitor banks or other energy
storage systems would have to be used.
Tests have been conducted to build stealth surface ships based on the technology
developed for the F-117 Nighthawk stealth fighter. The first such system was built by the USA
Navy as “The Sea Shadow.”
Figure 33. The Sea Shadow stealth ship used radar deflecting technology used in the F-117
Nighthawk stealth fighter. Source: USAF.
Figure 34. Lockheed-Martin RQ-170 Sentinel Stealth Unmanned Aerial Vehicle (UAV) drone,
known as the Beast of Kandahar. Source: Lockheed-Martin.
Figure 35. To hide it from satellite imaging, the Sea Shadow stealth ship was moored under the
canopy of the “Hughes Miner Barge” that was allegedly used to retrieve a section of a sunken
Russian submarine with possibly its code machine and weapons systems.
Figure 36. Stealth radar deflecting technology implemented into a French Lafayette class frigate,
2001.
FREE ELECTRON LASER, FEL TUNABLE LASER
The Free Electron laser is contemplated as a directed energy weapon system that can
replace the radar-guided Phalanx gun used for close-in ship defense and used against rocket and
mortar attacks.
Lasers require a medium to turn light into a directed energy beam. Solid state lasers use
crystals. Chemical lasers use gaseous media. These two types generate the lasers at a specific
wave length. The chemical lasers use toxic chemical reactants such as ethylene and nitrogen
trifluoride.
Free Electron Lasers (FELs) do not need a gain medium and use a stream of energetic
electrons to generate variable wave length lasers. An FEL system can adjust its wavelength for a
variety of task and to cope with different environmental conditions. It can also run from a
vessel’s electrical power supply rather than its own, and does not need to stop and reload. Such a
system for naval vessel needs to have a power of 100 kW. More than that would be needed to
counter anti-ship ballistic missiles.
The tunable laser is a desirable feature since particles in the sea air like condensation can
reduce the effectiveness of a defined wavelength laser. The Free Electron laser can fire can fire
at different points along the spectrum picking out the frequency that would penetrate the moist
air.
The FEL is composed of a relativistic electron tube that uses an oscillator and an open
optical resonator running at 10 percent efficiency. An electron beam is injected into a high gain
amplifier series of alternating magnets called a “wiggler.” In the wiggler, the electron beam
bends or wiggles back and forth undrgoimg acceleration and emitting coherent laser radiation.
It can be used for multiple uses, for instance as a sensor for detection and tracking when
it is not used to hit an incoming missile. It could also be used for location, time-of-flight
location, information exchange, communications, for target location and for disruption of radar
and communications.
Electrical generators planned in the all-electric fleet can have a capacity of about 2 MW
of power, and can easily provide the future MW level of power to the FEL, particularly if more
than one generator is installed on a given ship.
ELECTROMAGNETIC RAIL GUN
A 32 MJ rail gun can generate a projectile travelling 10 nautical miles in 6 minutes. A 64
MJ gun the projectile would travel 200 miles in six minutes.
A rail gun powered from a ship’s electrical supply can shoot 20 rocket propelled artillery
shells in less than a minute on targets 63 nautical miles away. Two rail guns would have the
firepower of a 640 persons artillery battalion.
A plasma armature method of propulsion is used where a plasma arc is generated behind
the metallic projectile along copper rails.
The rounds would travel at 6 km/sec. This means that the rounds fired per ship would
increase from 232 to 5,000. These inert rounds also travel at around Mach 7, carrying a large
amount of kinetic energy at double the energy of conventional explosive shells. The force of the
projectile hitting a target have been compared to hitting a target with a medium size car at 380
mph.They would also travel farther to 200-300 nautical miles.
Each projectile would cost about $1,000, whereas a cruise missile would cost about
$1,000,000. A ship can have thousands of the small projectiles stored on board instead of just ab
out 100 cruise missiles.
HIGH POWERED MICROWAVE, HPM DIRECTED BEAMS
A “defense-suppression mission” involves taking out air defenses, radars, missile
launchers and command centers. It can be achieved by degrading, damaging or frying their
electronics using directed microwave beams.
Directed energy microwave weapons have been successfully used to destroy buried
Improvised Explosive Devices (IEDs) in Iraq.
ANTISUBMARINE WARFARE, ASW
Submarines are vulnerable to deep underwater nuclear explosions. Anti Submarine
Warfare (ASW) uses conventional torpedoes as well as nuclear devices. The Wigwam nuclear
underwater test was conducted on May 15, 1955. It used an underwater 30 kT TNT-equivalent
charge. It took place 450 miles SW of San Diego, California in the open ocean. The device had
to be reinforced for operation at the large pressures encountered at great water depth. It was a
large 8,250 lbs (5,700 lbs when submerged) B7 Betty depth charge suspended with 2,000 feet
cable from a floating barge. A shock wave resulted with the fireball rising to the water surface.
Figure 37. Wigwam B3 Betty nuclear depth charge test in open water off San diego, California.
May 15, 1955.
Figure 38. Nuclear B57 depth charge Anti Submarine Warfare (ASW) device.
A navy Lockheed S3 carrier-based aircraft was used as a delivery vehicle for both
conventional torpedoes and nuclear charges. It was used as aircraft carrier ASW defense. It was
equipped with a surface search radar and could drop sono-buoys submarines listening devices.
Figure 39. The Navy Lockheed S3 ASW aircraft has been withdrawn from service.
A side effect of underwater shock waves is the oceanographic effect of bottom bounce.
In this case, a sound wave would be reflected or refracted from water layers of different salinities
or temperatures. It could be reflected back from the ocean’s bottom and can divert uncontrolled
substantial amounts of energy miles away on subsurface and surface floating structures.
APPENDIX
SHIPPINGPORT PRESSURIZED WATER REACTOR AND LIGHT WATER
BREEDER REACTOR
The Shippingport power station, first operated in December 1957 and was the first USA’s
commercial nuclear power reactor operated by the Duquesne Light Company. It was a
pressurized water reactor with the first two reactor cores as “seed and blanket” cores. The seed
assemblies had highly enriched uranium plate fuel clad in zirconium, similar to submarine cores,
and the blanket assemblies had natural uranium.
The first core, PWR-1, had 32 seed assemblies with each seed assembly including four
subassemblies for a total of 128. Each subassembly contained 15 fuel elements for a total of
1920. The U235 loading for the first seed core 75 kgs and the subsequent seeds had 90 kgs
loadings.
Figure 1. Shippingport Reactor PWR-1 seed subassembly showing the highly enriched
zirconium clad fuel and coolant channels. Dimensions in inches.
Figure 2. Cross section of Shippinport PWR-1 core showing the seed region and the blanket
regions A, B, C and D.
Figure 3. Shippingport reactor blanket fuel assembly.
The PWR-1 blanket fuel was made of natural uranium in the form of natural UO2 pellets
clad with Zircaloy tubes. Each blanket assembly was made from seven stacked fuel bundles.
Each fuel bundle was an array of short Zircaloy tubes with natural uranium oxide pellets in the
tubes. PWR-1 had 113 blanket assemblies each containing seven fuel bundles for a total of 791,
and each bundle contained 120 short fuel rods for a total of 94,920. The natural uranium loading
for the blanket fuel was 12,850 kgs of natural uranium.
Subsequently, the Shippingport blanket was replaced by a thorium control assembly to
introduce the light water breeder concept where U233 is bred from Th232 in a thermal neutron
spectrum.
EXERCISE
1.
For a reactor fueled with U235,
reactivity for equilibrium xenon.
REFERENCES
=2.42, p= 0.8,
=1.05, calculate the value for the
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2. John Lamarsh, “Introduction to Nuclear Engineering,” Addison-Wesley Publishing
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